High mortality rate in a re‐introduced grey partridge population in central Italy

Abstract

A radio-tracking study was carried out on a re-introduced population of grey partridges in a 10.6-km 2 study area located in central Italy, in order to assess mortality rate and to evaluate the feasibility of carrying out large scale re-introductions of the species. Thirty-nine grey partridges were caught by live-traps during winter 2000 and equipped with backpack radio-transmitter. All released birds were offspring of partridges re-introduced previously on the study area and no significant differences were found in survival probabilities between sexes, age classes (juveniles or adults), and weight classes (<400 g or 400 g), with the exception of the juveniles-adult comparison with the weight class 400 g. Kaplan-Meier estimates give an average survival of 734 days (SE = 15.5). GLM analysis showed an overall interaction effect of the sex, age, and weight (P = 0.03). Mortality increased during the covey break up, if compared to other periods, although the differences were not significant; the same was for males, for adults, and for both weight classes, while significant differences resulted for female and juvenile survival rate among periods. Predation was the main mortality source for radio-tagged grey partridges (71.0%), followed by disease (25.8%). The high mortality rate found in our study could be explained in part with the origin of the population that was originally re-introduced using hand-reared grey partridges. Some important negative characters of reared birds, such as the poor anti-predator behaviour and the low diseases resistance, could carry over during the first and following wild generations.

How do different releasing techniques affect the survival of reintroduced grey partridges Perdix perdix?

“…Negative effects may be caused by: 1) decreasing breeding success of wild birds that pair with reared birds (Rands & Hayward 1987), 2) attracting predators (Kenward 1981, Robertson 1988) and enhancing their interest in catching galliforms instead of other prey (Mueller 1971, Costantini et al 2005); however, DeVos & Speake (1995) did not find increased mortality of wild bobwhites after the release of artificially reared birds, 3) degrading genetics (Sage et al 2001, Ford 2002, Meriggi et al 2002, 4) genetic pollution (Barbanera et al 2007, Barilani et al 2007, Puigcerver et al 2007, and 5) increasing prevalence of parasites (Milla´n et al 2004, Villanua et al 2008. The use of medication in reared stocks may leave birds immunologically vulnerable when challenged by pathogens in the wild (Dowell 1992).…”

“…Moreover, the offspring of artificially reared galliforms that hatched in the wild have inferior survival and reproduction than truly wild birds (Woodburn 2001, Meriggi et al 2002. Dowell (1990a) released 8-9 week old grey partridges from natural, semi-natural (with hens) and artificial rearing.…”

Monitoring the survival rate of released chukars: a case study inElmalı Cedar Forest, Antalya, Turkey

“…Therefore, we assumed that these individuals had died. Previous studies have also found low survival rates in released partridges and most argued that, even if released birds survived to reach sexual maturity, their reproductive success would be very low (Putaala and Hissa, 1998;Meriggi et al, 2002;Duarte et al, 2011;Rymesova et al, 2013). This provides further support for rejecting stock enhancement as a tool to protect partridge populations.…”

“…Putaala and Hissa (1998) claim that released birds can only minimally contribute to the wild population due to their low survival and reproduction rates. Rymesova et al (2013), for example, recorded a mean lifespan of 14 ± 1.89 weeks with a minimum of 1 day and maximum of 78 days for 75 released partridges, while Meriggi et al (2002) reported 36.7 ± 6.0 weeks (min: 3 days, max: 94 days).…”

Demographic parameters of reintroduced grey partridges in central Italy and the effect of weather

“…The European populations of Grey partridge (Perdix perdix Linnaeus 1758) declined from mid-1950s onwards with the reduction and the marked fragmentation of their historical range, especially along the range boundaries (Potts 1986;Potts and Aebischer 1994;Putaala and Hissa 1998;Meriggi et al 2002;Aebischer and Ewald 2004;De Leo et al 2004;Panek 2005;Meriggi et al 2007). Population decreases occurred to such an extent that the species was considered threatened and vulnerable and was classified in the list of the Species of European Conservation Concern in the third category (i.e.…”