Strong effects of radio‐tags, social group and release date on survival of reintroduced grey partridges

Abstract

Animal reintroductions are important tools for conservation but often fail for reasons poorly understood. Biological and methodological factors can affect reintroduction success in complex manners. Investigating dispersal after release often relies on the use of biologging devices but individuals cope differently with these devices. They can detrimentally affect the performance of individuals depending on life‐history stage and may provide flawed conclusions, because inference drawn from tagged individuals cannot be readily generalized to non‐tagged individuals. Furthermore, environmental conditions during the release period or the expression of social behaviour such as the coordination of flocking behaviour can affect the outcome of reintroductions. In a reintroduction project involving 1385 grey partridges (Perdix perdix) released in 54 social groups (i.e. coveys), we investigated whether individual biweekly post‐release survival varied throughout different life‐history stages and was affected by radio‐tags of different weight (8 vs. 11 g), covey affiliation and release date. We conducted experiments in captivity to evaluate whether physiological stress, body condition and individual take‐off performance were affected by radio‐tags. During the first month after release survival was low in radio‐tagged and untagged birds. Throughout the second‐ and third‐month post‐release, negative effects of radio‐tags on survival were apparent. Four months after release, the survival of radio‐tagged and untagged birds converged. Consequently, the annual survival of untagged birds was more than five times higher than that of radio‐tagged birds. We did not find clear negative effects of radio‐tags on stress hormone levels but take‐off performance tended to be lower in tagged birds. Survival strongly decreased with later release date and differed between coveys. The use of radio‐tags can detrimentally affect individual survival and reintroduction success of grey partridges. The risk and benefits of radio‐tags should be balanced and releases in reintroductions should be conducted under the most favourable social and environmental conditions.

Diel cycle in a farmland bird is shaped by contrasting predation and human pressures

“…Captive-reared partridges usually also demonstrate shorter dispersal distances than wild ones (Rymesova et al, 2013). While we found that non-survivors had a lower diffusion rate from the release site than survivors, the captive-reared origin of birds may also have contributed to an increase in mortality within released population, as well as GPS devices (Homberger et al, 2021) though this does not seem to be the case in our study (Appendix 4). Generations of captive breeding may also affect bird morphology and physiology (e.g.…”

Chick survival and hunting are important drivers for the dynamics of two Alpine black grouse Lyrurus tetrix populations

“…Radio tagging on galliformes may negatively affect their survival (Bro et al 1999, Buner and Schaub 2008, Homberger et al 2021). As negative effects are expected to occur immediately after tagging, we have excluded individuals that disappeared within two weeks after tagging.…”

Herkomstbepaling van patrijs in Vlaanderen

“…Belangrijk hierbij te vermelden is dat verschillende studies (vb. Angelov et al 2019, Buner 2009, Buner et al 2011, Homberger et al 2021, Rymešová et al 2013) aantonen dat zowel de overlevingskansen als het broedsucces van gekweekte patrijzen in het wild zeer laag zijn (zie Mergeay et al 2022 voor een samenvatting). Daarnaast kunnen uitgezette patrijzen die afkomstig zijn van wildvang op basis van genetische analyses niet gedetecteerd worden als uitgezette exemplaren.…”