The abundance of yellow-legged gulls Larus michahellis breeding in the historic centre of Venice, Italy and the initial effects of the new waste collection policy on the population

Francesca Coccon,Lorenzo Vanni,Caterina Dabalà,Dimitri Giunchi

doi:10.1007/s11252-021-01175-7

Abstract

The yellow-legged gull Larus michahellis has undergone widespread colonization of the urban environment in the recent past. The first urban breeding gulls were recorded in the historical centre of Venice, Italy, in 2000, and by 2005 there were already 24 roof-nesting pairs, with this number increasing significantly over the last decade. In 2016, a new door-to-door garbage collection system was introduced in Venice to prevent the accumulation of rubbish in the streets and limit the trophic resources available for the species. This study provides an up-to-date estimate of the Venice yellow-legged gull urban population using distance sampling method. We also studied the effect of the new waste collection system on the species by comparing the population estimate before (2017) and after (2018) the full implementation of this change and by analysing the trend of individuals collected in the old town by the wildlife recovery service during 2010–2018. Results estimated ca. 430 breeding pairs in June 2018 showing a 36% decrease with respect to 2017. We also found a decrease in the number of 1-year-old birds and pulli collected by the wildlife recovery service starting from 2016, when the policy implementation began. Our data did not show a significant decrease in the overall number of individuals, suggesting that the new policy has a stronger effect on the breeding success of the species than on adult survival. This study emphasizes the importance of preventing rubbish accumulation in the streets as factor for reducing the abundance of urban yellow-legged gulls.

Highlights

Over the centuries, and from the beginning of the industrial revolution, humankind has profoundly transformed the Earth’s surface by converting the original landscape into anthropic ecosystems, mainly represented by urban areas and farm fields (Meyer and Turner 1992; Houghton 1994; Berry 2008), generating major pressures on other life forms and exerting selective pressures which drive the evolution of many species (Alberti et al 2003; Ellis 2015; Albuquerque et al 2018)
In this work we provided an updated estimate of the yellowlegged gull population in the historic centre of Venice and investigated the initial effects of the new waste collection system on the species by comparing the abundance of individuals and breeding pairs when the policy change affected only a part of the city and when it was implemented in all the districts, as well as by analysing the trend of yellow-legged gulls collected in the city centre by the wildlife recovery service over an eight-year period
We updated the estimate of the urban population of yellow-legged gulls for the historic centre of Venice using distance sampling (Buckland et al 2001) applied to counts performed from elevated vantage points, a novel monitoring method for the species in urban environment

Summary

Introduction

From the beginning of the industrial revolution, humankind has profoundly transformed the Earth’s surface by converting the original landscape into anthropic ecosystems, mainly represented by urban areas and farm fields (Meyer and Turner 1992; Houghton 1994; Berry 2008), generating major pressures on other life forms and exerting selective pressures which drive the evolution of many species (Alberti et al 2003; Ellis 2015; Albuquerque et al 2018). Urban Ecosystems from the beginning of the century to the mid-1970s (Raven and Coulson 1997; Coulson 2015) and the yellow-legged gull Larus michahellis showed a clear demographic growth in Italy, by increasing from 24,000–27,000 breeding pairs in 1983 (Meschini and Frugis 1993) to the 45,000–60,000 in the early 2000s (Brichetti and Fracasso 2006). Overall, this species has undergone a widespread population explosion over the past 30 years in the whole Mediterranean basin (Vidal et al 1998). In France, the first urban-nesting gulls were recorded in 1970 (Cadiou 1997), while in Spain they were recorded in 1975 (Petit et al 1986)

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Conclusion