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Habitat selection and ontogeny of habitat use by juvenile Eurasian Spoonbill Platalea leucorodia revealed by GPS tracking

Published online by Cambridge University Press:  16 September 2022

Manuela S. Rodrigues*
Affiliation:
DBIO & CESAM, University of Aveiro, Campus Universitário de Santiago, 3800 Aveiro, Portugal University of Coimbra, MARE – Marine and Environmental Sciences Centre / ARNET - Aquatic Research Network, Department of Life Sciences, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
Pedro M. Araújo
Affiliation:
University of Coimbra, MARE – Marine and Environmental Sciences Centre / ARNET - Aquatic Research Network, Department of Life Sciences, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, 4485-661 Vairão, Portugal
João P. Silva
Affiliation:
CIBIO/InBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Campus Agrário de Vairão, Universidade do Porto, 4485-661 Vairão, Portugal
José M. Abad-Gómez
Affiliation:
Conservation Biology Research Group, Department of Anatomy, Cell Biology and Zoology, Faculty of Sciences, University of Extremadura, Badajoz, Spain
Pedro C. Rodrigues
Affiliation:
Escola Superior de Educação & inED, Instituto Politécnico do Porto, Rua Dr. Roberto Frias 602, 4200-465 Porto, Portugal
Jaime A. Ramos
Affiliation:
University of Coimbra, MARE – Marine and Environmental Sciences Centre / ARNET - Aquatic Research Network, Department of Life Sciences, Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
José A. Alves
Affiliation:
DBIO & CESAM, University of Aveiro, Campus Universitário de Santiago, 3800 Aveiro, Portugal University of Iceland, South Iceland Research Centre, 840 Laugarvatn, Iceland
*
*Author for correspondence: Manuela S. Rodrigues, Email: [email protected]
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Summary

Despite the widely recognized value of wetlands in providing vital ecosystem services, these are presently being degraded and ultimately destroyed, leading to a decrease in the biodiversity associated with these areas. Some species inextricably linked to wetlands, however, have been increasing and (re)colonizing areas across their range; a notable example being the Eurasian Spoonbill Platalea leucorodia. In this study we aimed to identify the most important habitats for juvenile spoonbills fledging from a traditional colony in Portugal, located in Ria Formosa, during the period of their life with the lowest survival rates: the first months after leaving the colony. We deployed 16 GPS/GSM tags on juveniles captured in different years (2016 to 2020) and tracked them during post-fledging dispersal and first winter (average 166.4 ± 29.2 SE days). Using Corine Land Cover data, we were able to identify which habitats were most important. Several habitats were used in variable proportions by individuals originating from the same colony, but there was a general trend towards using fewer habitats along the first months of life. Intertidal wetlands were the most used habitat, but anthropogenic habitats such as Wastewater Treatment Plants, saltpans and rice fields were identified as alternative habitats for young spoonbills, and may had contributed to the recent expansion of this species in Portugal.

Type
Research Article
Copyright
© The Author(s), 2022. Published by Cambridge University Press on behalf of BirdLife International

Introduction

Wetlands are highly productive natural systems (Tiner Reference Tiner1989, Keddy Reference Keddy2010) that provide multiple ecosystem services such as climate regulation, nutrient cycling, and provisioning of food and freshwater (M.E.A. 2005, Nellemann and Corcoran Reference Nellemann and Corcoran2010). However, some studies estimate that at least 50% of the world’s wetlands have been destroyed (M.E.A. 2005, Davidson Reference Davidson2014), with Europe presenting the highest value: 75% of all wetlands disappeared over the last 100 years (Owen Reference Owen2007). The main reason for such destruction is the conversion of wetlands into agricultural and industrial areas, but also water drainage, and indirect pollution from agricultural, industrial and urban effluents (Van Asselen et al. Reference van Asselen, Verburg, Vermaat and Janse2013, Dodman et al. Reference Dodman, Citegetse, García Moreno, van Kleunen, van Roomen, van Roomen, Nagy, Citegetse and Schekkerman2018). Due to wetland degradation, many waterbird species declined and changed their distribution range (Luthin Reference Luthin1987, Boere et al. Reference Boere, Galbraith, Stroud and Thompson2006, Okes et al. Reference Okes, Hockey and Cumming2008). However, since the1980s some of these species began to recover, showing positive population trends and recolonizing areas within their distribution range, despite only marginal restoration of wetlands (Wetlands International 2016). European wetlands received more protection in recent decades owing to the Water Framework Directive (2000/60/EC). Several waterbirds, however, began to recover long before the implementation of this directive, which suggests alternative causes for population recovery.

Understanding the habitat requirements of these species is fundamental for their conservation, particularly in critical phases of their lives, in order to establish sound management plans. Altricial birds that are fed by parents after hatching, experience the highest mortality following independence (Sullivan Reference Sullivan1989, Daunt et al. Reference Daunt, Afanasyev, Adam, Croxall and Wanless2007, Lok et al. Reference Lok, Overdijk, Tinbergen and Piersma2013b). And one of the main factors for this high mortality during the first months after independence is low foraging efficiency and consequent starvation, either by inefficient searching and/or handling proficiency, competition with adults, or low ability to locate suitable feeding patches (Wunderle Reference Wunderle1991, Kershner et al. Reference Kershner, Walk and Warner2004, Daunt et al. Reference Daunt, Afanasyev, Adam, Croxall and Wanless2007). Juveniles often show a different spatial and temporal ecology from adults (Goss-Custard et al. Reference Goss-Custard, Durell, McGrorty and Reading1982, Wunderle Reference Wunderle1991, Kershner et al. Reference Kershner, Walk and Warner2004), either by displaying preferences towards different habitats (Fayet et al. Reference Fayet, Freeman, Shoji, Padget, Perrins and Guilford2015), exploring wider areas (Zango et al. Reference Zango, Navarro-Herrero, García-Vendrell, Safi and González-Solís2020) or by foraging for longer periods (Daunt et al. Reference Daunt, Afanasyev, Adam, Croxall and Wanless2007). It is therefore important to better understand habitat use during this critical phase to better inform the conservation of waterbird species during such key life stage.

The population of Eurasian Spoonbill Platalea leucorodia, like other migratory waterbird species, decreased drastically in Europe in the early 20th century, and by 1950 only two breeding colonies were still active: one in Spain and other in the Netherlands (Triplet et al. Reference Triplet, Overdijk, Smart, Nagy, Schneider-Jacoby, Karauz and Pigniczki2008). After intense recovery programmes, the East Atlantic population (that breeds along the East Atlantic European coast and winters from France to coastal West Africa, as south as Senegal) is currently increasing (Overdijk Reference Overdijk and Navedo2013, Champagnon et al. Reference Champagnon, Pigniczki and Kralj2019), and the species is now classified as ‘Least Concern’ (LC) in the European Red List (BirdLife International 2015). The (re)colonization of breeding areas is currently ongoing in Europe and, in most cases, this occurred following habitat conversion or restoration at traditional breeding locations (Tucakov Reference Tucakov2004, Marion Reference Marion and Navedo2013, Ramo et al. Reference Ramo, Aguilera, Figuerola, Máñez and Green2013). In Portugal, despite the existence of few historical breeding records from the 17th century (Tait Reference Tait1924), the species was classified as a non-breeder until 1988, when the first successful breeding event was registered in Paúl do Boquilobo (Pereira Reference Pereira1989). Since then, the breeding population of spoonbills increased from 43 pairs in 1996 (Farinha and Encarnação Reference Farinha, Encarnação and Aves1996, Equipa Atlas Reference Atlas2008) to 540 in 2014 (Farinha and Trindade Reference Farinha and Trindade1994, Farinha and Encarnação Reference Farinha, Encarnação and Aves1996, Equipa Atlas Reference Atlas2008, Encarnação Reference Encarnação2014) and expanded northwards. The number of breeding colonies also increased to 10, as recently as 2014 (Encarnação Reference Encarnação2014), when the newest colony in the country was established.

Juvenile spoonbills fledge between 35 and 54 days (Cramp and Simmons Reference Cramp and Simmons1977, Triplet et al. Reference Triplet, Overdijk, Smart, Nagy, Schneider-Jacoby, Karauz and Pigniczki2008), and during the post-fledging period perform exploratory movements in the vicinity of the colony, that can reach distances of more than 100 km (Hancock et al. Reference Hancock, Kushlan and Kahl1992, Aguilera Reference Aguilera1997, Volponi et al. Reference Volponi, Emiliani and Fasola2008, Jelena et al. Reference Jelena, Antun, Tibor and Otto2012). Following this period, juveniles either migrate to southern wintering areas or remain in the vicinity of the colony, particularly birds originating from southern Europe (Bauchau et al. Reference Bauchau, Horn and Overdijk1998, Triplet et al. Reference Triplet, Overdijk, Smart, Nagy, Schneider-Jacoby, Karauz and Pigniczki2008, Volponi et al. Reference Volponi, Emiliani and Fasola2008, Lok et al. Reference Lok, Overdijk and Piersma2013a). To understand the habitat requirements of juvenile spoonbills during a key phase of their life, (after leaving the breeding colony), we attached GPS/GSM tags to pre-fledglings from a Portuguese colony (Ria Formosa, Algarve) and tracked their movements and ontogeny of habitat use up to their first year of life. Our specific objective was to identify the most important habitats for juvenile spoonbills during their dispersal phase from the natal colony. This information is essential for the development of conservation strategies that may benefit this and other waterbird species with similar ecological requirements.

Methods

Fieldwork was carried out in the Ria Formosa Natural Park (36°59’N, 7°55’W), a lagoon system separated from the Atlantic Ocean by a system of small islands and sandbanks composed by several habitats such as marshes, fresh and brackish lagoons, saltpans, dune banks and agricultural fields (Figure 1). The Ria Formosa Natural Park was established in 1987, later becoming a Special Protection Areas (SPA) for birds under the European Bird Directive (2009/147/EC), being thus part of Natura 2000 Network, and is also a Ramsar site since 1981. Even though Ria Formosa has historically been an important area for spoonbills, both as wintering and as a stopover site, the species only started breeding locally in 1993, in a small marsh island within the lagoon (Farinha and Trindade Reference Farinha and Trindade1994). This spoonbill breeding colony has its limits established by the water line around the island at low tide and during the study period the number of nests fluctuated between 66 and 116 (in 2018 and 2020, respectively; J. Silvério pers. comm.).

Figure 1. A) and B) Location of Ria Formosa colony in Portugal (star) and representation of the Minimum convex polygon (MCP – dashed black line) considering all locations attained from juvenile spoonbills in the vicinity of Ria Formosa during pre-winter (see text for details); C) Locations of three selected juvenile spoonbills tracked with GPS/GSM tags in Ria Formosa during pre-winter, and the location of the wastewater treatment plant (WWTP) most used by spoonbills.

From 2016 to 2020 we captured 16 pre-fledglings (two in 2016, five in 2017, four in 2018, two in 2019 and three in 2020; Table 1) from the nests by hand (making sure such procedure was harmless to the bird) and tagged them with solar-powered GPS/accelerometer GSM tags (Movetech Telemetry, www.movetech-telemetry.com) attached using a backpack harness made of Teflon ribbon. We recorded biometric measurements (tarsus and head/bill length) to back-calculate hatch date based on Lok et al. (Reference Lok, Overdijk and Piersma2014). Chicks were measured and selected for tagging based on their development stage (35 ± 2 SE days). The weight of the tags, harness and rings was 33 g, thus below the 3% threshold of the body mass of the tagged spoonbills (mean body mass 1,524 ± 217.53 g; n = 16) to avoid adverse effects (Phillips et al. Reference Phillips, Xavier and Croxall2003, Casper Reference Casper2009). Tracked spoonbills were named instead of simply using a code (Table1). Tags recorded a burst of 10 seconds of GPS fix (with an associated error of ≤3 m) and 3D accelerometer data at 1 Hz every 30 minutes. We kept only one GPS point per burst and removed GPS locations that used less than four satellites for geopositioning to avoid uncertainty. Accelerometer data were used to determine probable mortality events when inactivity was recorded, and to confirm flying fixes as indicated by the GPS metadata, that were removed from the present analysis. During most of the nocturnal period (between 21h00 and 05h00) only one GPS fix was collected at 01h00 to save battery. QGIS, version 3.10, combined with R software (R Core Team 2019), version 3.6, were used to perform all the spatial data analysis and visualization of geographical data.

Table 1. Tracking details of juvenile spoonbills from Ria Formosa equipped with GPS/GSM tags.

Habitat selection and usage

All analyses of habitat use start when juvenile spoonbills left the colony for the last time, i.e. when no subsequent returns to the colony where recorded. We defined this period as After Leaving the Colony (ALC). The last position of each spoonbill considered for analysis was the last location of the bird (when it either died or the tag failed) or the last location in Europe (if the bird migrated to Africa), until the maximum period of one year since chick hatching.

To study habitat usage by juvenile spoonbills we used Corine Land Cover 2018 (CLC), with data accessible from Copernicus Land Cover monitoring services (Bossard et al. Reference Bossard, Feranec and Otahel2000). The CLC map was complemented with satellite images (Google 2020) to reclassify incorrectly classified points due to cell size. CLC identifies 44 land use types and those present in the study area were grouped into higher levels of organization resulting in six final habitat categories (Table 2). We excluded from the analysis a few fixes that occurred in urban areas (n = 32; 0.06%), considering those to be an error in GPS localization.

Table 2. Corine land cover (CLC) corresponding to habitat categories analysed.

To assess how the use of different habitats varied for each individual ALC we quantified the weekly frequency of usage of each habitat by dividing the number of locations in a given habitat in a week, by the total number of locations in that week. Because juveniles in their first year are likely to be exploratory, we did a revisitation analysis to identify the most important habitats for juvenile spoonbills, using the package ‘Recurses’ in R (Bracis et al. Reference Bracis, Bildstein and Mueller2018). This package allows calculation of the number of times the trajectory of an individual enters a circular area centred in each position of the trajectory, that is, how many times one individual revisits the same location. As we did not know which habitats were revisited the most, nor the activities performed in those areas by spoonbills, we did not have any a priori consideration of the size of the radii to use in order to define the area around locations. Hence, we did a preliminary analysis of radius size, testing radii ranging from 10 m to 1,000 m through a sensitivity analysis (see Appendix S1 in the online supplementary material) and established that 100 m was appropriate, as higher values did not produce different results. We defined a minimum threshold of 60 minutes (between two consecutive locations) to ensure that revisitations were independent (if the individual left the defined radius but returned within 60 minutes, for example during a bout of foraging movements, it was not considered a new revisitation, but as part of the prior visit). We selected the locations that had a ratio of relocations in the 75th percentile of total relocations of each individual, as an indication that those were chosen as suitable to feed or rest (Bracis et al. Reference Bracis, Bildstein and Mueller2018) rather than only exploratory.

To evaluate if the most revisited habitats changed during the first year of life, we divided the study period into two, following the delimitation of yearly periods suggested for spoonbills from the nearest breeding colony in Odiel, Spain (Aguilera Reference Aguilera1997): a) “pre-winter”, defined as the period between ALC and 30 September, encompassing the more exploratory phase of juveniles, when large migratory movements are more likely to occur; and b) “winter”, from 1 October to 31 January. As we collected virtually no information from nine spoonbills (Nembus, Polaris, Dalim, Ascella, Mizar, Azha, Australis, Tabit and Enif) in winter in Europe, these individuals were excluded from the analysis for this second period.

In order to assess if habitats in Ria Formosa were used in accordance with their availability, we performed a second order selection of habitat (Johnson Reference Johnson1980). We estimated the availability of each habitat type comprised in the minimum convex polygon (MCP) of the positions of all spoonbills during “pre-winter”, when the majority of spoonbills remained in Ria Formosa, close to the breeding colony (excluding the positions of Polaris, Sirius Mizar, and Azha after they left the vicinity of Ria Formosa). We used the package ‘phuassess’ (Fattorini et al. Reference Fattorini, Pisani, Riga and Zaccaroni2017) in R, to test the probability of the null hypothesis being true, that is, habitats were used in the same proportion of their availability, thus being neither preferred or avoided (Aebischer et al. Reference Aebischer, Robertson and Kenward1993, Fattorini et al. Reference Fattorini, Pisani, Riga and Zaccaroni2014).

Results

GPS/GSM tags recorded on average 166.4 ± 29.2 SE days of tracking, with the maximum period corresponding to 16 months, and the minimum to 55 days, in cases when the bird died or the tag failed (Table 1). Spoonbills left the colony for the first time on average at 50.6 ± 1.8 SE days of life, and their final visit to the colony occurred at the age of 67.6 ± 3.98 SE days (Table 1). Of all the spoonbills tracked, five migrated to North Africa: Polaris, Ascella, Sirius (only in its second winter), Australis and Tabit, while the remaining birds stayed in Iberia. Seven spoonbills died during the tracking period. Survival in early winter varied between 0.31 and 0.62 until December (considering tag failure as either death or alive), and in late winter varied between 0.8 and 1 until March (with only one tag failure during the coldest months of the year). Mortality was identified by multiple overlapping GPS fixes in the same location, and confirmed by the 3D accelerometer showing static readings. Based on the accelerometer data we were able to determine date, and approximate hour of death. Because the analysis only started when spoonbills left the colony (ALC) and ended when either the juvenile died, migrated to Africa, or completed one year of life, the number of days considered for analysis is smaller than the total tracking period (on average: 120.3 days ± 25.83 SE, ranging from 10 to 297 days). Enif was thus excluded from the subsequent analysis as only 10 days of data were recorded after it left the colony (ALC). Each tag collected on average 23.23 ± 0.51 SE points per day, from which 20.88 ± 0.51 SE were collected during the day and 7.38 ± 0.42 SE during the night.

Habitat selection and usage

Juvenile spoonbills selected a broad range of habitats, with large variation between weeks (Figure 3). The most revisited habitats were intertidal wetlands (30.7%) followed by rice fields (27.5%) and saltpans (18.4%; Table 3a). However, when considering only the pre-winter period, Wastewater treatment plant (WWTP) was the most revisited habitat (35.9%), despite accounting for only 0.2% of the habitats present in the vicinity of colony within the area comprised by the MCP. This was followed by saltpans (26.9%), present in 5.8%, and by intertidal wetlands (24.2%), one of the most common habitats in the area (36.0%). Agricultural areas are the most available habitat, and rice fields and inland waters were absent of the 242.4 km2 (MCP) around the colony.

Table 3. Habitat use by juvenile spoonbills from a colony in Ria Formosa, Portugal: a) Percentage of juvenile spoonbills revisitation of each habitat type for the study periods (see text for details). Only locations with a ratio of relocations in the 75th percentile of total relocations of each individual were considered. b) Result of the second order habitat selection proposed by Fattorini et al. (Reference Fattorini, Pisani, Riga and Zaccaroni2014). Habitat type availability in Ria Formosa (restricted to the minimum convex polygon, see text for details) by juvenile spoonbills.

Overall, available habitats were thus not used in accordance with their availability (Table 3b). Intertidal wetlands (P = 0.27) and saltpans (P = 0.09) were used in proportion to their availability, whereas agricultural and other habitats (mostly urban areas) were avoided (both P < 0.01). WWTP was the only preferred habitat (P < 0.01). During winter, intertidal areas were the most important habitat (33.4%), followed by saltpans (27.8%) and rice fields (25.9%). In total, anthropogenic habitats available in the vicinity of the colony accounted for 64.0% of the area comprised within the MCP, whereas this was only 36.0% for natural habitats. Anthropogenic areas (created and/or manipulated by humans, including saltpans, WWTP, rice fields and other agricultural areas), were used more than natural areas (56.9% vs 43.1%). In addition, during pre-winter, this difference was even larger, as 63.0% of the revisited habitats are classified as anthropogenic.

When considering annual tendencies (Figure 3), saltpans were used more in the first years of the study period (annual percentage in chronological order: 37.7%, 25.5%, 20.9%, 1.2%, 4.2%) and intertidal wetlands in the most recent years (annual percentage in chronological order: 42.1%, 25.9%, 66.0%, 56.4%, 83.5%). WWTP were used in all years but only until November whereas rice fields started to be used only in October.

Individual habitat usage fluctuated considerably during the first weeks following ALC (Figure 2). For individuals tracked more than 20 weeks, it appears that between week 12 (Castor) and 20 (Mira) two habitats became clearly dominant, with their usage being mirrored, and all other habitats becoming considerable reduced (Figure 2). This pattern was also apparent for some individuals from a much earlier stage (e.g. Atlas, Rigel and Hadar, from week 2).

Figure 2. Frequency of habitat usage by tracked spoonbill juveniles from Ria Formosa per week, starting after leaving the colony (ALC) for the last time.

Figure 3. Percentage of habitat usage of each spoonbill in each month. Years are referenced to aid comparisons.

Discussion

Habitat selection and usage

Juvenile spoonbills born in Ria Formosa rely not only on intertidal habitats but also on anthropogenic habitats, such as saltpans, rice fields and Wastewater treatment plants. The importance of intertidal wetlands, a category that encompasses several natural habitats (Table 2), was to be expected since it is well known that spoonbills use these for obtaining food. For example, in the Wadden Sea, spoonbills mainly feed their chicks with marine prey instead of freshwater prey (Jouta et al. Reference Jouta, De Goeij, Lok, Velilla, Camphuysen, Leopold, Van Der Veer, Olff, Overdijk and Piersma2018). Also in the German Wadden Sea, both adults and juveniles selected tidal creeks for foraging during breeding and post-breeding (Enners et al. Reference Enners, Guse, Schwemmer, Chagas, Voigt and Garthe2020). In our study, we did not differentiate habitat usage by behaviour, and this may explain the utilization of a larger array of habitat types that fulfil other requirements, like roosting. Alternatively, the use of different habitats may be a function of their availability since anthropogenic habitats were very common in the study area (Table 3). Nevertheless, such habitats appeared to be a good substitute for natural ones, considering the survival found in our study, which did not differ substantially from the results from a well-studied population (early winter: 0.31–0.62 vs 0.33 ± 0.03 CI and late winter: 0.8–1 vs 0.58 ± 0.05 CI; Lok et al. Reference Lok, Overdijk, Tinbergen and Piersma2013b). It should be noted that there are two WWTPs (the only preferred habitat) in the area: Faro-Olhão (the most used by spoonbills in this study) and Olhão-Poente; both with maturation ponds that are extensively used by several species of waterbirds all the year around (Matos et al. Reference Matos, Ramos, Calado, Ceia, Hey and Paiva2018, Rias Reference Rias2019). This is a known alternative habitat for waterbirds, including spoonbills (Frederick and McGehee Reference Frederick and McGehee1994, van Dijk and Bakker Reference van Dijk and Bakker1998, Newman and Lindsey Reference Newman and Lindsey2011) that may be attracted by the constant water levels. Nonetheless, juveniles using these areas may be more exposed to pathogens and toxins such as those causing botulism outbreaks (Hamilton Reference Hamilton2007, Murray and Hamilton Reference Murray and Hamilton2010), not only due to the presence of these substances in the water but also because of the usual large congregation of birds in these sites that facilitates the propagation of diseases (Anza et al. Reference Anza, Vidal, Laguna, Díaz-Sánchez, Sánchez, Chicote and Florín2014). Interestingly, this habitat was not used in winter which leads to the question of why this apparently suboptimal habitat was used by juveniles in pre-winter. It is possible that continued water availability in WWTP explains this since its usage coincides with the driest season, when water levels are lowest in more natural habitats, or it may be related to density-dependence factors. The period when WWTP was most used (pre-winter) coincided with the period of highest abundance of spoonbills in the south of Portugal (Alves et al. Reference Alves, Lourenço, Dias, Antunes, Catry, Costa and Fernandes2012), potentially also reflecting the lower capacity of juveniles to compete for the most favourable natural habitats (Goss-Custard et al. Reference Goss-Custard, Durell, McGrorty and Reading1982, Cresswell Reference Cresswell1994, Durell Reference Durell2000).

Saltpans were often revisited in pre-winter, but also in winter, and are a common habitat in Ria Formosa. These habitats may be suitable for juveniles since they also have managed water levels, with some being used to produce salt and others converted to aquaculture. In fact, saltpans replaced coastal wetlands in many areas throughout the world, and constitute an important habitat for many waterbird species (Rufino et al. Reference Rufino, Araujo, Pina and Miranda1984, Velasquez Reference Velasquez1992, Warnock et al. Reference Warnock, Page, Ruhlen, Nur, Takekawa and Hanson2002), including spoonbills (Aguilera et al. Reference Aguilera, Ramo and Court1996, Fonseca et al. Reference Fonseca, Grade and Cancela da Fonseca2004, Pigniczki and Végvári Reference Pigniczki and Végvári2015).

Rice fields were only used in winter, and even though this was one of the most revisited habitats, it was only used by two individuals, Vega and Sirius, which dispersed beyond Ria Formosa lagoon system, where rice fields are absent. Vega dispersed to the west of Ria Formosa and Sirius to Spain. During pre-winter they were not used, likely due to the hot and dry autumn in the Iberia peninsula which often leaves rice paddies totally dry in autumn and completely dependent on precipitation patterns. Rice fields have been widely identified as substitute foraging habitat for waterbirds (Fasola and Ruiz Reference Fasola and Ruiz1996, Czech and Parsons Reference Czech and Parsons2002), mostly when flooded, which in the Iberian peninsula occurs especially during winter and migratory periods (Elphick Reference Elphick2000, Alves et al. Reference Alves, Lourenço, Piersma, Sutherland and Gill2010, Toral and Figuerola Reference Toral and Figuerola2010). Despite rice fields being an alternative habitat for waterbirds, usually most species prefer natural areas when available (Campos and Lekuona Reference Campos and Lekuona2001, Tourenq et al. Reference Tourenq, Bennetts, Kowalski, Vialet, Lucchesi, Kayser and Isenmann2001). However, the fact that rice fields had a lot of revisitations only by two individuals, and was the main habitat revisited by Vega, may indicate that it can also be a good substitute habitat for juvenile spoonbills, at least in winter.

Ontogeny of habitat use

In the first weeks after leaving the colony, the proportion in which each habitat was used varied among weeks and individuals. Still, considering over 20 weeks of tracking, a clear pattern of habitat selection emerges, showing a tendency towards each individual using only two habitat types. The decrease in the number of different habitats used during the weeks after leaving the colony may result from the start of a more specialized phase and the end of the most exploratory phase of the juvenile spoonbills, which occurs at the beginning of the post-fledging period. Alternatively, the use of a higher number of habitats in the initial months may be the result of higher competition with adults at the beginning of the post-fledging period, when more northerly breeders arrive in the area to spend the non-breeding season or to refuel on their way to Africa, potentially leading juveniles to spread over several habitats (Goss-Custard et al. Reference Goss-Custard, Durell, McGrorty and Reading1982, Wunderle Reference Wunderle1991, Cresswell Reference Cresswell1994). Juvenile spoonbills’ patterns of habitat use were very diverse across the entire study period but also within each study year. The fact that some juveniles were able to use habitats less used by others may suggest competition avoidance (Bolnick et al. Reference Bolnick, Svanbäck, Fordyce, Yang, Davis, Hulsey and Forister2003, Araújo et al. Reference Araújo, Bolnick and Layman2011). On the other hand, given that they were able to exploit several different habitat types, it suggests that this species may cope relatively well with habitat change and even habitat loss (Durell Reference Durell2000), at least in areas where alternative anthropogenic habitats can buffer the loss of natural areas. In fact, other studies already suggested an opportunistic foraging behaviour by spoonbills (El-Hacen et al. Reference El-Hacen, Piersma, Jouta, Overdijk and Lok2014, Enners et al. Reference Enners, Guse, Schwemmer, Chagas, Voigt and Garthe2020) and our study also seems to corroborate that. The fact that saltpans were mostly used by juveniles born in 2016–2018 and less used by juveniles born in 2019–2020 may indicate that in those early years, saltpans had more attractive conditions. Unfortunately, we do not have information on water levels on those habitats to be able to assess this. It may also be a consequence of the small sample size in each year, which limits the variation between individuals. Another result that suggests opportunistic habitat use by juvenile spoonbills is the difference between the three spoonbills that remained in Ria Formosa (Castor, Hadar and Mira) and the two that remained in the Iberian Peninsula but left the vicinity of the colony (Vega and Sirius). The first group used the same two habitats in different proportions (Figure 2): saltpans and intertidal wetlands (two available habitats in Ria Formosa), while the second group used other two different habitats: inland waters and rice fields (not available in Ria Formosa). In fact, rice fields only started being used by tracked spoonbills in October, most likely when these start being flooded, once Sirius had already dispersed to areas with rice fields by August, but only started using them in October. Polaris went to the same area as Sirius but migrated to Africa in September, which likely explain why it did not use rice fields.

One limitation of our work was the absence of extended nocturnal tracking, especially when studying the use of intertidal wetlands, but the use of those areas may be more limited by tidal movements than by daylight hours, and since the study spanned several months, the results should present little tidal bias. In order to better understand drivers of differences in habitat usage along the first year of independence, it would be important to obtain information relative to the use and habitat selection of adult spoonbills, to test if competition may be forcing juveniles into poorer habitats. Moreover, it will be important to quantify water availability in several habitat types and its variability throughout the year, to ascertain if juveniles are using anthropogenic habitats due to water scarcity in natural habitats. Furthermore, determining which activities are performed in different habitats will likely provide a better interpretation of the current patterns of habitat usage, particularly in assessing if anthropogenic habitats are used for foraging or mostly for other activities (e.g. roosting, preening, etc.)

In summary, we show that juveniles are able to use several habitat types, including anthropogenic habitats, which supports the idea that the development of spoonbill colonies in Portugal is driven, at least partially, by the capacity of individuals of this species to explore new habitat types (Shultz et al. Reference Shultz, Bradbury, Evans, Gregory and Blackburn2005), which was also the case in Serbia, where spoonbills are now using fish farms (Tucakov Reference Tucakov2004). This work highlights the need to further protect and restore natural intertidal wetlands but also to identify and manage anthropogenic habitats important to spoonbills. The fact that anthropogenic habitats were used by spoonbills, which is considered a specialist species (Swennen and Yu Reference Swennen and Yu2005, Pigniczki Reference Pigniczki2017), highlights their opportunistic behaviour on habitat selection and may indicate that these habitats can also be favourable to other waterbird species with similar ecology.

Acknowledgements

We are grateful to Ria Formosa’s wardens, Silvério and Capela, for the help with the fieldwork and for monitoring the colony. To Vitor Encarnação for the information about Portuguese colonies, and to all the people that helped in the fieldwork. We thank the reviewers whose suggestions contributed to improving this work. We received the support of Portuguese national funds provided by ‘Fundação para a Ciência e a Tecnologia, I.P.’ (FCT/MCTES), to MSR (SFRH/BD/145942/2019), JAA (SFRH/BPD/91527/2012), through the strategic project UIDB/04292/2020 granted to MARE, through project LA/P/0069/2020 granted to the Associate Laboratory ARNET, and through UIDP/50017/2020+UIDB/50017/2020+ LA/P/0094/2020 granted to CESAM. Permits for bird sampling issued by the national authority for wild bird handling & ringing ICNF were granted to JAA (113/2016, 119/2017, 97/2018) and PMA (202/2015, 189/2018, 191/2020).

Supplementary Materials

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References

Aebischer, N. J., Robertson, P. A. and Kenward, R. E. (1993) Compositional analysis of habitat use from animal radio-tracking data. Ecology 74: 13131325.CrossRefGoogle Scholar
Aguilera, E. (1997) Dispersal and migration in Eurasian spoonbills Platalea leucorodia. Ardea 85: 193202.Google Scholar
Aguilera, E., Ramo, C. and Court, C. d. l. (1996) Food and feeding sites of the Eurasian spoonbill (Platalea leucorodia) in southwestern Spain. Colon. Warterbirds: 159166.Google Scholar
Alves, J. A., Lourenço, P. M., Dias, M. P., Antunes, L., Catry, T., Costa, H., Fernandes, P., et al. (2012) Monitoring waterbird populations on the Tejo, Sado and Guadiana estuaries, Portugal: 2011 report. Anuário Ornitológico (SPEA) 9: 6687.Google Scholar
Alves, J. A., Lourenço, P. M., Piersma, T., Sutherland, W. J. and Gill, J. A. (2010) Population overlap and habitat segregation in wintering Black-tailed Godwits Limosa limosa. Bird Study 57: 381391.CrossRefGoogle Scholar
Anza, I., Vidal, D., Laguna, C., Díaz-Sánchez, S., Sánchez, S., Chicote, Á., Florín, M., et al. (2014) Eutrophication and bacterial pathogens as risk factors for avian botulism outbreaks in wetlands receiving effluents from urban wastewater treatment plants. Appl. Environ. Microb. 80: 42514259.CrossRefGoogle ScholarPubMed
Araújo, M. S., Bolnick, D. I. and Layman, C. A. (2011) The ecological causes of individual specialisation. Ecol. Lett. 14: 948958.CrossRefGoogle ScholarPubMed
Bauchau, V., Horn, H. and Overdijk, O. (1998) Survival of spoonbills on Wadden Sea islands. J. Avian Biol. 29: 177182.CrossRefGoogle Scholar
BirdLife International (2015) European Red List of Birds. Luxembourg: Office for Official Publications of the European Communities.Google Scholar
Boere, G. C., Galbraith, C. A., Stroud, D. A. and Thompson, D. B. A. (2006) The conservation of waterbirds around the world. Pp. 3245 in Waterbirds around the world. Edinburgh, UK.: The Stationery Office.Google Scholar
Bolnick, D., Svanbäck, R., Fordyce, J., Yang, L., Davis, J., Hulsey, D. and Forister, M. (2003) The ecology of individuals: incidence and implications of individual specialization. Am. Nat. 161: 128.CrossRefGoogle ScholarPubMed
Bossard, M., Feranec, J. and Otahel, J. (2000) CORINE land cover technical guide: Addendum 2000.Google Scholar
Bracis, C., Bildstein, K. L. and Mueller, T. (2018) Revisitation analysis uncovers spatio-temporal patterns in animal movement data. Ecography 41: 18011811.CrossRefGoogle Scholar
Campos, F. and Lekuona, J. M. (2001) Are rice fields a suitable foraging habitat for Purple Herons during the breeding season? Waterbirds 24: 450452.CrossRefGoogle Scholar
Casper, R. (2009) Guidelines for the instrumentation of wild birds and mammals. Anim. Behav. 78: 14771483.CrossRefGoogle Scholar
Champagnon, J., Pigniczki, C. and Kralj, J. (2019) An overview of Eurasian Spoonbill trends. IUCN-SSC Stork, Ibis and Spoonbill Specialist Group Special Publication 2: 9.Google Scholar
Cramp, S. S. and Simmons, K. E. L. (1977) Handbook of the birds of Europe, the Middle East, and North Africa: the birds of the Western Palearctic. Vol 1: Ostrich-ducks. Oxford: Oxford University Press.Google Scholar
Cresswell, W. (1994) Age-dependent choice of redshank (Tringa totanus) feeding location: profitability or risk? J. Anim. Ecol. 63: 589600.CrossRefGoogle Scholar
Czech, H. A. and Parsons, K. C. (2002) Agricultural wetlands and waterbirds: A review. Waterbirds 25: 5665.Google Scholar
Daunt, F., Afanasyev, V., Adam, A., Croxall, J. and Wanless, S. (2007) From cradle to early grave: juvenile mortality in European shags Phalacrocorax aristotelis results from inadequate development of foraging proficiency. Biol. Lett. 3: 371374.CrossRefGoogle ScholarPubMed
Davidson, N. C. (2014) How much wetland has the world lost? Long-term and recent trends in global wetland area. Mar. Freshw. Res. 65: 934941.CrossRefGoogle Scholar
Dodman, T., Citegetse, G., García Moreno, J., van Kleunen, A. and van Roomen, M. (2018) Pressures and conservation measures for waterbirds along the East Atlantic Flyway. In van Roomen, M., Nagy, S., Citegetse, G., and Schekkerman, H. eds. East Atlantic Flyway assessment 2017: the status of coastal waterbird populations and their sites. Wilhelmshaven, Germany: Wadden Sea Flyway Initiative p/a CWSS.Google Scholar
Durell, S. E. L. V. D. (2000) Individual feeding specialisation in shorebirds: population consequences and conservation implications. Biol. Rev. 75: 503518.CrossRefGoogle Scholar
El-Hacen, E.-H. M., Piersma, T., Jouta, J., Overdijk, O. and Lok, T. (2014) Seasonal variation in the diet of Spoonbill chicks in the Wadden Sea: a stable isotopes approach. J. Ornithol. 155: 611619.CrossRefGoogle Scholar
Elphick, C. S. (2000) Functional equivalency between rice fields and seminatural wetland habitats Conserv. Biol. 14: 181191.Google Scholar
Encarnação, V. (2014) Monitoring waterbird colonies. Lisbon: ICNB.Google Scholar
Enners, L., Guse, N., Schwemmer, P., Chagas, A. L., Voigt, C. C. and Garthe, S. (2020) Foraging ecology and diet of Eurasian spoonbills (Platalea leucorodia) in the German Wadden Sea. Estuar. Coast. Shelf Sci. 233: 106539.CrossRefGoogle Scholar
Atlas, Equipa (2008) Breeding bird Atlas for Portugal (1999-2005). Lisboa: ICNB, SPEA, PNM e SRAM. Assírio & Alvim.Google Scholar
Farinha, J. C. and Encarnação, V. (1996) Estado actual das colónias de colhereiro Platalea leucorodia em Portugal. Pp. 7071 in Aves, S. P. p. o. E. d.. ed. Actas do I Congresso de Ornitologia. Vila Nova de Cerveira.Google Scholar
Farinha, J. C. and Trindade, A. (1994) Contribuição para o Inventário e Caracterização de Zonas Húmidas em Portugal Continental. Lison: Publicação MEDWET/Instituto da Conservação da Natureza.Google Scholar
Fasola, M. and Ruiz, X. (1996) The value of rice fields as substitutes for natural wetlands for waterbirds in the Mediterranean Region. Colon. Waterbirds 19: 122128.CrossRefGoogle Scholar
Fattorini, L., Pisani, C., Riga, F. and Zaccaroni, M. (2014) A permutation-based combination of sign tests for assessing habitat selection. Environ. Ecol. Stat. 21: 161187.CrossRefGoogle Scholar
Fattorini, L., Pisani, C., Riga, F. and Zaccaroni, M. (2017) The R package “phuassess” for assessing habitat selection using permutation-based combination of sign tests. Mamm. Biol. 83: 6470.CrossRefGoogle Scholar
Fayet, A. L., Freeman, R., Shoji, A., Padget, O., Perrins, C. M. and Guilford, T. (2015) Lower foraging efficiency in immatures drives spatial segregation with breeding adults in a long-lived pelagic seabird. Anim. Behav. 110: 7989.CrossRefGoogle Scholar
Fonseca, V. G., Grade, N. and Cancela da Fonseca, L. (2004) Patterns of association and habitat use by migrating shorebirds on intertidal mudflats and saltworks on the Tavira Estuary, Ria Formosa, southern Portugal. Wader Study Group Bull 105: 5055.Google Scholar
Frederick, P. C. and McGehee, S. M. (1994) Wading bird use of wastewater treatment wetlands in central Florida, USA. Colon. Warterbirds 17: 5059.CrossRefGoogle Scholar
Google (2020) Ria Formosa, Portugal. CNES, Aerodata International Surveys IGP, Airbus Landsat, DGRF Maxar technologies, Copernicus.Google Scholar
Goss-Custard, J. d., Durell, S. L. V. D., McGrorty, S. and Reading, C. (1982) Use of mussel Mytilus edulis beds by oystercatchers Haematopus ostralegus according to age and population size. J. Anim. Ecol. 51: 543554.CrossRefGoogle Scholar
Hamilton, A. J. (2007) Potential microbial and chemical hazards to waterbirds at the Western Treatment Plant. Ecol. Manag. Restor. 8: 3841.CrossRefGoogle Scholar
Hancock, J., Kushlan, J. A. and Kahl, M. P. (1992) Storks, ibises and spoonbills of the world. London: Academic Press.Google Scholar
Jelena, K., Antun, Ž., Tibor, M. and Otto, O. (2012) Movements of immature Eurasian Spoonbills Platalea leucorodia from the breeding grounds of the Eastern metapopulation in the Pannonian Basin. Waterbirds 35: 239247.CrossRefGoogle Scholar
Johnson, D. H. (1980) The comparison of usage and availability measurements for evaluating resource preference. Ecology 61: 6571.CrossRefGoogle Scholar
Jouta, J., De Goeij, P., Lok, T., Velilla, E., Camphuysen, C. J., Leopold, M., Van Der Veer, H. W., Olff, H., Overdijk, O. and Piersma, T. (2018) Unexpected dietary preferences of Eurasian Spoonbills in the Dutch Wadden Sea: spoonbills mainly feed on small fish not shrimp. J. Ornithol. 159: 839849.CrossRefGoogle Scholar
Keddy, P. A. (2010) Wetland ecology: principles and conservation. UK: Cambridge University Press.CrossRefGoogle Scholar
Kershner, E. L., Walk, J. W. and Warner, R. E. (2004) Postfledging movements and survival of juvenile Eastern Meadowlarks (Sturnella magna) in Illinois. The Auk 121: 11461154.CrossRefGoogle Scholar
Lok, T., Overdijk, O. and Piersma, T. (2013a) Migration tendency delays distributional response to differential survival prospects along a flyway. Am. Nat. 181: 520531.CrossRefGoogle ScholarPubMed
Lok, T., Overdijk, O. and Piersma, T. (2014) Interpreting variation in growth of Eurasian Spoonbill chicks: disentangling the effects of age, sex and environment. Ardea 102: 181194.CrossRefGoogle Scholar
Lok, T., Overdijk, O., Tinbergen, J. M. and Piersma, T. (2013b) Seasonal variation in density dependence in age-specific survival of a long-distance migrant. Ecology 94: 23582369.CrossRefGoogle ScholarPubMed
Luthin, C. S. (1987) Status of and conservation priorities for the world’s stork species. Colon. Warterbirds 10: 181202.CrossRefGoogle Scholar
M.E.A. (2005) Ecosystems and human well-being: wetlands and water. Washington, DC: World Resources Institute.Google Scholar
Marion, L. (2013) Recent trends of the breeding population of Spoonbill in France Pp. 3843 in Navedo, J. ed. Proceedings of the Eurosite VII Spoonbill Workshop.Google Scholar
Matos, D. M., Ramos, J. A., Calado, J. G., Ceia, F. R., Hey, J. and Paiva, V. H. (2018) How fishing intensity affects the spatial and trophic ecology of two gull species breeding in sympatry. ICES J. Mar. Sci. 75: 19491964.CrossRefGoogle Scholar
Murray, C. G. and Hamilton, A. J. (2010) Perspectives on wastewater treatment wetlands and waterbird conservation. J. Appl. Ecol. 47: 976985.CrossRefGoogle Scholar
Nellemann, C. and Corcoran, E. (2010) Dead planet, living planet: biodiversity and ecosystem restoration for sustainable development. United Nations Environment Programme (UNEP).Google Scholar
Newman, M. and Lindsey, A. (2011) A ten-year study of herons, spoonbills and ibis at the Morpeth Wastewater Treatment Works near Maitland in NSW. Whistler 5: 1018.Google Scholar
Okes, N. C., Hockey, P. A. and Cumming, G. S. (2008) Habitat use and life history as predictors of bird responses to habitat change. Conserv. Biol. 22: 151162.CrossRefGoogle ScholarPubMed
Overdijk, O. (2013) The remarkable recovery of the North Atlantic Spoonbill breeding population. Pp. 912 in Navedo, J. ed. Proceedings of the Eurosite VII Spoonbill Workshop.Google Scholar
Owen, P. (2007) LIFE and Europe’s wetlands: restoring a vital ecosystem. Luxembourg: Office for Official Publications of the European Communities.Google Scholar
Pereira, F. (1989) Garcas e afins na Reserva Natural do Boquilobo. Pp. 1524. Livro de de Resumos 1° Encontro Ornitológico do Paul da Tornada. Caldas da Rainha.Google Scholar
Phillips, R. A., Xavier, J. C. and Croxall, J. P. (2003) Effects of satellite transmitters on albatrosses and petrels. The Auk 120: 10821090.CrossRefGoogle Scholar
Pigniczki, C. (2017) Dispersal and migration of a specialist waterbird: where do Eurasian Spoonbills (Platalea leucorodia) come to Hungary from? Ornis Hungarica 25: 124.CrossRefGoogle Scholar
Pigniczki, C. and Végvári, Z. (2015) Dispersal of the Central European population of the Eurasian Spoonbill Platalea leucorodia. Ardeola 62: 219236.CrossRefGoogle Scholar
R Core Team (2019) R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing.Google Scholar
Ramo, C., Aguilera, E., Figuerola, J., Máñez, M. and Green, A. J. (2013) Long-term population trends of colonial wading birds breeding in Doñana (SW Spain) in relation to environmental and anthropogenic factors. Ardeola 60: 305326.CrossRefGoogle Scholar
Rias, C. d. r. e. i. d. a. s. (2019) Monitorização ambiental das Etar Faro-Olhão e Olhão Poente.Google Scholar
Rufino, R., Araujo, A., Pina, J. P. and Miranda, P. S. (1984) The use of salinas by waders in the Algarve, South Portugal. Wader Study Group Bull. 42: 4142.Google Scholar
Shultz, S., Bradbury, R. B., Evans, K. L., Gregory, R. D. and Blackburn, T. M. (2005) Brain size and resource specialization predict long-term population trends in British birds. Proc. Royal Soc. B: Biol. Sci. 272: 23052311.CrossRefGoogle ScholarPubMed
Sullivan, K. A. (1989) Predation and starvation: age-specific mortality in juvenile juncos (Junco phaenotus). J. Anim. Ecol. 58: 275286.CrossRefGoogle Scholar
Swennen, C. and Yu, Y.-T. (2005) Food and feeding behavior of the black-faced spoonbill. Waterbirds 28: 1927.CrossRefGoogle Scholar
Tait, W. C. (1924) The birds of Portugal. London: Witherby.Google Scholar
Tiner, R. W. (1989) Wetlands of Rhode Island. Newton Corner: F. a. W. Service.Google Scholar
Toral, G. M. and Figuerola, J. (2010) Unraveling the importance of rice fields for waterbird populations in Europe. Biodivers. Conserv. 19: 34593469.CrossRefGoogle Scholar
Tourenq, C., Bennetts, R. E., Kowalski, H., Vialet, E., Lucchesi, J.-L., Kayser, Y. and Isenmann, P. (2001) Are ricefields a good alternative to natural marshes for waterbird communities in the Camargue, southern France? Biol. Conserv. 100: 335343.CrossRefGoogle Scholar
Triplet, P., Overdijk, O., Smart, M., Nagy, S., Schneider-Jacoby, M., Karauz, E., Pigniczki, C., et al. (2008) International single species action plan for the conservation of the Eurasian Spoonbill Platalea leucorodia. Bonn: AEWA Tech. Ser.Google Scholar
Tucakov, M. (2004) Changes of breeding numbers and habitat of Eurasian Spoonbill Platalea leucorodia in Vojvodina (N Serbia). Acrocephalus 25: 7178.Google Scholar
van Asselen, S., Verburg, P. H., Vermaat, J. E. and Janse, J. H. (2013) Drivers of wetland conversion: A global meta-analysis. PloS One 8: e81292.CrossRefGoogle Scholar
van Dijk, K. and Bakker, T. (1998) Dutch Spoonbills platalea leucorodia and a Finnish Turnstone Arenaria interpres on tropical islands: counts of shorebirds in the Cape Verdes in March 1996. Wader Study Group Bull 86: 4043.Google Scholar
Velasquez, C. (1992) Managing artificial saltpans as a waterbird habitat: species’ responses to water level manipulation. Colon. Warterbirds 15: 4355.CrossRefGoogle Scholar
Volponi, S., Emiliani, D. and Fasola, M. (2008) An overview of spoonbills in Italy. Eurosite Spoonbill Network Newsletter 5: 35.Google Scholar
Warnock, N., Page, G. W., Ruhlen, T. D., Nur, N., Takekawa, J. Y. and Hanson, J. T. (2002) Management and conservation of San Francisco Bay salt ponds: effects of pond salinity, area, tide, and season on Pacific Flyway waterbirds. Waterbirds 25: 7992.Google Scholar
Wetlands International (2016) Waterbird population estimates. wpe.wetlands.org.Google Scholar
Wunderle, J. M. (1991) Age-specific foraging proficiency in birds. Curr. Ornithol. 8: 273324.Google Scholar
Zango, L., Navarro-Herrero, L., García-Vendrell, M., Safi, K. and González-Solís, J. (2020) Niche partitioning and individual specialization among age, breeding status and sex classes in a long-lived seabird. Anim. Behav. 170: 114.CrossRefGoogle Scholar
Figure 0

Figure 1. A) and B) Location of Ria Formosa colony in Portugal (star) and representation of the Minimum convex polygon (MCP – dashed black line) considering all locations attained from juvenile spoonbills in the vicinity of Ria Formosa during pre-winter (see text for details); C) Locations of three selected juvenile spoonbills tracked with GPS/GSM tags in Ria Formosa during pre-winter, and the location of the wastewater treatment plant (WWTP) most used by spoonbills.

Figure 1

Table 1. Tracking details of juvenile spoonbills from Ria Formosa equipped with GPS/GSM tags.

Figure 2

Table 2. Corine land cover (CLC) corresponding to habitat categories analysed.

Figure 3

Table 3. Habitat use by juvenile spoonbills from a colony in Ria Formosa, Portugal: a) Percentage of juvenile spoonbills revisitation of each habitat type for the study periods (see text for details). Only locations with a ratio of relocations in the 75th percentile of total relocations of each individual were considered. b) Result of the second order habitat selection proposed by Fattorini et al. (2014). Habitat type availability in Ria Formosa (restricted to the minimum convex polygon, see text for details) by juvenile spoonbills.

Figure 4

Figure 2. Frequency of habitat usage by tracked spoonbill juveniles from Ria Formosa per week, starting after leaving the colony (ALC) for the last time.

Figure 5

Figure 3. Percentage of habitat usage of each spoonbill in each month. Years are referenced to aid comparisons.

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