The return of raptors to Scotland’s skies: Investigating the diets of reintroduced red kites and white-tailed eagles using stable isotopes

Waterman, Juliette; Black, Stuart; Sykes, Naomi; Kitchener, Andrew C; Mills, William F; Fellowes, Mark D E

The return of raptors to Scotland’s skies: Investigating the diets of reintroduced red kites and white-tailed eagles using stable isotopes

Download

Name

journal.pone.0315945.pdf

Description

visibility:open

Size

1.52 MB

Format

Adobe PDF

Checksum (CRC64NVME)

LID8i7kLKi8=

Resource type

Journal article

Creator (person)

Waterman, Juliette

ORCID

Black, Stuart

Sykes, Naomi

Kitchener, Andrew C

ORCID

Mills, William F

ORCID

Fellowes, Mark D E

ORCID

Date published

January 8, 2025

Abstract

Species reintroductions are increasingly seen as important methods of biodiversity restoration. Reintroductions of red kites and white-tailed eagles to Britain, which were extirpated in the late 19 and early 20 centuries, represent major conservation successes. Here, we measured stable isotope ratios of carbon ( C) and nitrogen ( N) in feather keratin and bone collagen of museum specimens of red kites and white-tailed eagles, which were collected from across Scotland between the 1800s and 2010s. Our objectives were to investigate dietary differences between species and between the pre- and post- reintroduction periods. Among reintroduced birds, C values were significantly less negative and N values higher in feather keratin and bone collagen of white-tailed eagles compared to red kites, likely reflecting a greater reliance on marine resources by the former. Our stable isotope data showed a wide range, confirming the dietary diversity observed in conventional diet studies of both taxa, with white-tailed eagles, in particular, having wide dietary niches and a considerable degree of inter-individual variability. Isotopic data from pre-introduction red kites mostly fell within the range of post-reintroduction birds, suggesting they had similar diets to the pre-reintroduction birds, or the prey base for modern birds is isotopically indistinguishable from that of their historic counterparts. For white-tailed eagles, several pre-reintroduction birds were isotopically distinct from the post-reintroduction population. These differences may indicate a changing prey base, although these conclusions are complicated by shifting distributions and small population samples. Overall, our study demonstrates the utility of natural history collections in examining changes in diet, environment, and interactions with humans in reintroduced species compared with pre-extirpation indigenous populations.

Contributor (person)

Drucker, Dorothée