Uso del espacio por adultos de gaviota patiamarilla Larus michahellis Naumann, 1840 durante el periodo reproductor: resultados preliminares en relación al uso de vertederos.

Abstract

ResumenEn la actualidad, con el progresivo cierre de vertederos, nos situamos en un marco experimental ideal para estudiar cómo afecta la reducción drástica de un recurso trófico en la ecología, dinámica poblacional y movimientos de una especie con alto interés en la gestión, como es la gaviota patiamarilla Larus michahellis Naumann, 1840. En este contexto, en 2016 se equiparon con GPS un total de 10 ejemplares adultos de gaviota patiamarilla en una de las colonias de cría de Gipuzkoa, de los que sólo 4 proporcionaron datos hasta el 31.07.2016. El análisis preliminar aporta información básica sobre el uso del territorio durante una parte del periodo reproductor. El porcentaje de localizaciones se distribuyó de esta manera: 60% en la colonia; 18% en otro tipo de hábitats; 12% en prados y cultivos; y 6.5% en vertederos. Se detecta, así, un relativo alto uso de los prados y cultivos del entorno de la colonia, así como de dos de los vertederos más importantes de la región. Por otro lado, parece existir alta variabilidad individual en el uso del territorio que podría reflejar diferentes estrategias en la búsqueda de alimento.Palabras clave: Dispositivos GPS, ecología espacial, especies oportunistas, Gipuzkoa, vertederos. AbstractToday, the progressive closure of landfills provides a good opportunity to study how this affects the drastic reduction of a food resource on the ecology, population dynamics and movement patterns of opportunistic species, such as the yellow-legged gull Larus michahellis Naumann, 1840. Against this background, in 2016, we captured 10 adult breeding gulls in one of the main breeding colonies in Gipuzkoa. These individuals were equipped with a GPS device. Only four of them provided data up to the end of the breeding period (31.07.2016). Preliminary analyses provide basic information about spatial use and trophic habitat during the breeding period (colony: 60%; other habitat types: 18%; grasslands/crops: 12%; dumps: 6,5%). An apparently relatively high use of grasslands and crops is confirmed, as well as the use of two of the largest landfills in the region. We also observed a very high individual variation in territory use, which might reflect different foraging strategies.Key words: GPS device, spatial ecology, opportunistic species, Gipuzkoa, dumps. LaburpenaEgun, urratsez urrats zabortegiak ixten ari direlarik, testuinguru esperimental ezin hobean gaude ikertzeko nola eragiten dion baliabide trofiko baten erabateko murrizketak maila ekologikoan, populazio dinamikan eta mugimenduetan, baliabide horren kudeaketarekin lotura handia duen kaio hankahoriari, Larus michahellis Naumann, 1840.

Evaluating the effect of distance to different food subsidies on the trophic ecology of an opportunistic seabird species

“…However, preliminary data from GPS‐tracked birds have shown only marginal use of built‐up areas (<20%, with> 90% of these being in terms of roosting places, such as roofs of industrial unit, river banks known to be used to rest, etc). Arizaga et al () and more unpublished data). It is therefore likely that prey consumption from built‐up areas was small in this study and hence that the percentage of prey estimated to originate in ‘landfill’ was correct.…”

Evaluating the dependence of opportunistic Yellow‐legged Gulls (Larus michahellis) on marine habitat and fishing discards

“…Getaria's breeding population is estimated at 165 adult breeding pairs (in 2017) and it has a positive growth rate (Arizaga et al . 2014, Zorrozua et al . 2020b).…”

“…S1; Zorrozua et al 2020a). Getaria's breeding population is estimated at 165 adult breeding pairs (in 2017) and it has a positive growth rate (Arizaga et al 2014, Zorrozua et al 2020b). Ulia's population comprises 660 breeding pairs (in 2017) and is the largest colony in Gipuzkoa.…”

“…These food subsidies have direct implications at ecosystem, community, animal population and individual levels (Hidalgo-Mihart et al 2004, Olea & Baglione 2008, Weiser & Powell 2010, Oro et al 2013, Steigerwald et al 2015, Gilbert et al 2016. Landfills, for instance, can have a large impact on movement ecology and territory use, trophic ecology, and demographic or toxicological aspects for several opportunistic species, such as vultures, storks and gulls (Auman et al 2008, de la Casa-Resino et al 2014, Arizaga et al 2017, Shaffer et al 2017, Ackerman et al 2018, Plaza & Lambertucci 2018, Langley et al 2021. Dependence on these PAFS can stimulate sedentary strategies or decrease dispersal distances (Gilbert et al 2016), improve survival and reproduction, and, overall, promote population growth (Duhem et al 2008, Weiser & Powell 2010.…”

High philopatry rates of Yellow-legged Gulls in the southeastern part of the Bay of Biscay

“…2a refers to models assuming a difference between two age categories (birds in their first year of life and older birds); 3a refers to models assuming a difference between birds in their first and second year, and older birds; 4a refers to models assuming a difference between birds up to their third-year of life (immatures), and older birds (adults). Given that most birds hatch by the end of May or early June (Arizaga et al 2012), a year was considered to last from June to the end of May of the subsequent year. To run such models: (1) we started by fixing ψ and S as constant and time dependent, and testing for the best options fitting on p. Alternative models were ranked in relation to their small sample sizecorrected Akaike values (AICc; Burnham and Anderson 1998); models differing in less than 2 AICc values were considered to fit to the data equally well (Burnham and Anderson 1998) ; (2) Once we found the model best fitting on p, we repeated a similar process on S, and, finally, on ψ.…”