Parental investment of male Peregrine Falcons during incubation: influence of experience and weather

Abstract

Incubation involves a transfer of heat between parent and embryo. The brood patch is pressed against one surface of the egg, and warming occurs as a result of adjustments in both blood flow through the brood patch and heat production by the parent. A brood patch normally develops in both sexes in bird species where incubation is biparental. But in uniparental species, where the male does not incubate, or in species where he contributes to incubation for short periods only (e.g. Peregrine Falcon), the brood patch is absent or poorly developed in males. Considering that male peregrines do not develop a brood patch, and by consequence have less efficient heat transmission capabilities, we tested four hypotheses related to the time devoted to incubation by male peregrines. This study was conducted on a long-term-monitored population located in northern Spain. We spent 482.73 h monitoring peregrine incubation events in 37 territories from 2008 to 2016. We observed 203 changeovers. Males relieved females 3.02 ± 2.61 times per day. The changeover rate was not regularly distributed throughout the daylight period. Males devoted 114.3 ± 84.24 min to each incubation event. The time invested by males in incubation was strongly related to their level of experience at breeding in the territory. However, there were no significant relationships between the time devoted by males to incubation and their previous accumulated reproductive success. Neither was there a relationship between reproductive performance and the time invested by males in incubation. The time that males devoted to incubation was significantly related to the environmental temperature. It seemed that males devoted nonsignificantly slightly less time to incubation during the first and last weeks of the incubation process. This results demonstrate that the uniparental scheduling in Peregrine Falcons is conditioned firstly by ambient factors and secondly by male experience.