Variation in breeding parameters of Eleonora's falcon (Falco eleonorae) and factors affecting its reproductive performance

Abstract

We gathered data for a four‐year period (2004–2007) on the nesting ecology and reproductive performance of Eleonora's falcon in the Aegean Sea. We investigated in an indirect way the relation between clutch size and pre‐laying food availability, the significance of site and pair quality on productivity, and the effects of habitat and intraspecific competition on breeding success. Overall, the species selected nest sites sheltered from sun exposure but not from the prevailing wind. Hatching, fledging, and breeding success rates were estimated at 64, 72%, and 60%, respectively. Fledglings per breeding pair ranged from 1.19 to 1.75, and fledglings per successful pair from 1.84 to 2.0, between the years. Productivity depended on parental care rather than nest‐site quality. Breeding parameters varied significantly between the years, exhibiting a strong spatial yet local effect. Low success rates were recorded in specific colonies, which were attributed to adverse weather conditions and habitat degradation. Insect food availability prior to egg‐laying, estimated via plant biomass, was positively correlated to clutch size. Meanwhile, low wind strengths in August, large distances from the mainland, and population size in the vicinity of the colonies had negative effects on breeding success. Considering data at the Mediterranean scale, a longitudinal trend is observed across the breeding range of this species, with breeding parameters slightly decreasing from west to east.

On the brink: status and breeding ecology of Eleonora’s FalconFalco eleonoraein Algeria

“…Nonetheless, contrasting results have been reported (Walter 1979, Wink et al 1982, Urios and Martínez-Abraín 2006), suggesting that wind exposure is probably not so decisive as to drive a preference for sheltered nests in this species. In contrast, predation pressure from mammal or avian predators, including conspecifics, could be of higher importance, because these can reach unprotected nests much more easily than protected ones (Ristow and Wink 1985, Xirouchakis et al 2012). Likewise, adults breeding in exposed nest-sites are more prone to momentarily abandon the nest due to disturbance, which also entails a high risk of clutch overheating.…”

Summer pre-breeding movements of Eleonora’s Falcon Falco eleonorae revealed by satellite telemetry: implications for conservation

“…Ristow (2001) showed that poison ingested by Eleonora’s Falcons through drinking at polluted pools inland in Crete caused several deaths and a strong decline in a close-by breeding colony. It has been also shown that insect availability prior to egg-laying, even near the colonies, can affect clutch size (Xirouchakis et al 2012). Therefore, events occurring in the pre-breeding staging areas could have serious consequences at the population level and it is thus of paramount importance to identify and protect at least the areas where the highest concentrations of Eleonora’s Falcons occur.…”

Sooty FalconFalco concolorreproduction and population dynamics on the islands in the Sea of Oman

“…Xirouchakis et al . () found a negative relationship between Eleonora's Falcon nesting success and distance to the mainland. We suggest that the higher nesting success rate and productivity observed on Fahal is largely the result of falcons being able to forage on the mainland, where food supply is relatively high, especially when prey birds are not migrating.…”

“…We discuss our results in the context of the late nesting characteristics of Sooty Falcons, and assess whether food availability and nearness to the mainland (Xirouchakis et al . ) may explain annual and island‐group variation in reproductive parameters.…”