We investigated the potential for released captive‐reared grey partridges Perdix perdix to restock regions from which the species has disappeared. Birds were released at two sites in Scotland (not concurrently) from 1997 to 2003 and monitored via spring and autumn counts, night‐time surveys and radio‐telemetry. Some wild female partridges were caught and radio‐tagged each spring for comparison with reared females. The survival rate of 520 captive‐reared birds released in autumn until the following spring was poor (around 10% overall) and was not significantly different for radio‐tagged and visibly‐marked birds. Carrying a radiotag did not alter the body condition of the birds. The breeding‐season survival rate of released hens averaged 30% and was not significantly different to that of 44% for wild hens. However, the power to detect significant differences was low due to the small number of survivors. The major cause of mortality throughout was predation (82 and 55% of losses at the two sites), with red foxes Vulpes vulpes and raptors being the most significant predators. Reared partridges at the study site with legal predator control had higher survival rates than those at the other site, but this was not true for wild hens as raptor predation compensated for declining mammalian predation rates (19% of deaths were due to raptors at the site without predator control, 56% at the site with predator control). We suggest that the vulnerability to predation of reared birds was most likely due to inappropriate antipredator behaviour or an increased risk of predation near to release pens. Of the partridges that survived long enough to breed, three times more wild hens reached incubation than reared hens. No reared hens raised chicks in their first breeding season whilst the only hen that survived long enough to breed in her second year raised 14 young. Captive‐reared grey partridges could not be used to increase the species' range unless 1) the number surviving their first year increased, 2) the higher breeding rate of two‐year‐old females suggested here was ubiquitous, and unless 3) appropriate management was in place first. Methods for improving the success of releases are discussed.

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We summarize key results of the first 53 years of one of the longest-running avian population studies in the world, on the Peregrine Falcon (Falco peregrinus), in the French Jura mountains (12,714 km2), launched in 1964. A total of 449 cliff sites in 338 potential Peregrine territories were surveyed: 287 (85%) of these territories were occupied by an adult pair at least once, while in 51 (15%) we never detected an adult pair. Most sites were visited several times during a breeding season to survey occupancy and later fecundity, but the proportion of sites visited was highly variable over the years. We highlight the power of the Bayesian implementation of site-occupancy models (MacKenzie et al. 2002, 2003) to analyze data from raptor population studies: to correct population size estimates for sites not visited in a given year and for the biasing effects of preferential sampling (when better sites are more likely to be checked). In addition, these models allow estimation and modeling of the site-level persistence and colonization rates, which can provide important clues about drivers of population dynamics, even without individually marking any birds. Changes in the dynamics rates may serve as early-warning signals for subsequent population declines. Since 1964, the observed number of adult pairs varied between 17 in 1972 and 196 in 2008, but the proportion of sites visited increased from 43% in 1964 to 80–90% after 2002. Hence, this raw population total must be an underestimate. We found strong evidence for preferential sampling in our study. Correcting for this, we estimated 56 pairs in 1964, after which the population dropped to a minimum of 18 in 1972, but then recovered rapidly, leveling off somewhat around 1995 and reaching a maximum of 200–210 adult pairs during 2000–2012. This was then followed by a decline to 170–190 pairs. In any one year, the raw counts underestimated the true population size by 5–39% (mean 11%), due to sites not being visited (this correction ignores imperfect detection though). Site persistence rates declined from 78% to less than 60% during 1967–1972, and then increased rapidly to over 90% during 1980–1990, suggesting that once pesticide effects vanished, individual survival probability increased rapidly and as a consequence also site persistence. Since the 1990s, persistence has declined slowly, which may indicate decreasing adult survival. In contrast, colonization rates increased steadily from about 3% in the early years to maxima of 46–49% during 1994–2001, but declined thereafter and currently reach about 33%. Taller cliffs had greater persistence and colonization rates than medium or small cliffs. Both the decline in colonization and in persistence rates during the last 15 years may reflect density-dependence, predation by the expanding European Eagle Owl (Bubo bubo) population, human persecution or any as yet unknown factors. Importantly, we note that both persistence and colonization rates began to decline many years before the recent population decline became apparent. Thus, analysis of population studies using dynamic occupancy models can provide early-warning signals for future population declines. Our study demonstrates the benefits of modern analytical methods that can correct for several key deficiencies in probably all raptor population studies: incomplete coverage of sites and imperfect detection (though we only dealt with the former here). Occupancy models, possibly accounting for preferential sampling, appear to represent the logical analytical framework for abundance in raptor population studies.