Context‐dependent conservation of the cavity‐nesting European Roller

Tom Finch,Edmunds Račinskis,Jamie Dunning,Harriet Clewlow,Timothée Schwartz,Claire Branston,Simon J Butler,Aldina M A Franco

doi:10.1111/ibi.12650

Tom Finch, Edmunds Račinskis + Show 6 more

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https://doi.org/10.1111/ibi.12650

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Abstract

To maximize the effectiveness of conservation interventions, it is crucial to have an understanding of how intraspecific variation determines the relative importance of potential limiting factors. For bird populations, limiting factors include nest‐site availability and foraging resources, with the former often addressed through the provision of artificial nestboxes. However, the effectiveness of artificial nestboxes depends on the relative importance of nest‐site vs. foraging resource limitations. Here, we investigate factors driving variation in breeding density, nestbox occupation and productivity in two contrasting study populations of the European Roller Coracias garrulus, an obligate cavity‐nesting insectivorous bird. Breeding density was more than four times higher at the French study site than at the Latvian site, and there was a positive correlation between breeding density (at the 1‐km2 scale) and nest‐site availability in France, whereas there was a positive correlation between breeding density and foraging resource availability in Latvia. Similarly, the probability of a nestbox being occupied increased with predicted foraging resource availability in Latvia but not in France. We detected no positive effect of foraging resource availability on productivity at either site, with most variation in breeding success driven by temporal effects: a seasonal decline in France and strong interannual fluctuations in Latvia. Our results indicate that the factors limiting local breeding density can vary across a species' range, resulting in different conservation priorities. Nestbox provisioning is a sufficient short‐term conservation solution at our French study site, where foraging resources are typically abundant, but in Latvia the restoration of foraging habitat may be more important.

Highlights

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not
Breeding density was more than four times higher at the French study site than at the Latvian site, and there was a positive correlation between breeding density and nest-site availability in France, whereas there was a positive correlation between breeding density and foraging resource availability in Latvia
We detected no positive effect of foraging resource availability on productivity at either site, with most variation in breeding success driven by temporal effects: a seasonal decline in France and strong interannual fluctuations in Latvia

Summary

Introduction

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. An added complication is that anthropogenic threats (Olea & Mateo-Tomas 2014), habitat associations (Whittingham et al 2007), population demography (Morrison et al 2016), vulnerability to local extinction (Yackulic et al 2011) and response to conservation interventions (Walker et al 2018) can vary across a species’ range, sometimes over relatively small spatial scales. To maximize the effectiveness of local conservation interventions, it is important to understand the mechanisms underlying resource limitation, but how these vary under different contexts This requires the use of consistent monitoring across space, allowing explicit intraspecific comparisons. Such intensive multi-site studies are currently rare (Morris et al 2001, but see e.g. O€ st et al 2016), with global inventories of threat typically generalizing within species (Birdlife International 2018) and conservation action plans often lacking detailed information on intraspecific variation (e.g. Kovacs et al 2008)

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