Behavioural and body mass changes before egg laying in the Barn Owl: cues for clutch size determination?

Abstract

To investigate laying decision and clutch size determination in indeterminate layers, we analysed in-nest activity (nest presence, and copulation, prey deliveries, and entrance frequencies) and female body mass change, as well as their relation to clutch size variation in five Barn Owl pairs (Tyto alba) nesting in eastern France. Body mass of the female and behaviour [copulation frequency, entrance frequency, and prey delivery to the nest by the male (in number and mass)] were monitored using an automated weighing system and a video camera. There was a consistent change of behaviour and foraging activity among pairs ca. 18 days before laying indicating that the females may be tied to the nest at this time. Barn Owls being indeterminate layers have their clutch size determined at the oviposition of the first egg of the clutch. Window correlation analyses between the clutch size and the female body mass gain indicate that the clutch size might be determined no later than a few days before the laying of the first egg. Our results suggest that female Barn Owls may use the pre-laying period to determine the clutch size using cues such as the male food deliveries (a proxy for male quality).

Barn Owl (Tyto alba) breeding biology in relation to breeding season climate

“…3). Given that Barn Owls may adjust clutch size according to the amount of food brought back by the male (Durant et al 2010), and that rain impairs hunting success, it is surprising that larger clutches were observed with increasing amounts of rainfall prior to laying. Rain has been shown to have a rapid impact on clutch size; Patten and Rotenberry (1999) found that more rain 1 and 3 months prior to clutch completion led to larger clutches in the Blue Tit, and Lloyd (1999) found that Greybacked Finchlarks (Eremopterix verticalis) produced larger clutches just 1 week after abundant rains.…”

Diel feeding strategy during breeding in male Barn Owls (Tyto alba)

“…Barn Owls have to fly over the surrounding houses to reach their nest from the hunting ground carrying their prey, which may be very heavy (e.g. Arvicola terrestris of 120 g compared to a Barn Owl mass of ca 300 g; Roulin, 2004) .The female Barn Owl usually lays clutches of 4-7 eggs depending on food availability (Durant, 2000;Durant et al, 2010;Muller, 1991). The female starts incubation after laying the 1 st egg of the clutch and stays in the nest continuously, thus depending on the male for her food supply (Bunn et al, 1982;Durant et al, 2004;Shawyer, 1994;Taylor, 1994) until she reinitiates foraging ca two weeks after hatching of the first egg (Durant, 2002;Durant et al, 2004;Taylor, 1994).…”

DIET PREFERENCES AND REPRODUCTION OF TRANSLOCATED BARN OWL, Tyto alba javanica IN CAPTIVITY

“…Marti (1994) has described the barn owl (Tyto alba) as having a higher biotic potential and more flexible reproduction than most other owls and ecologically similar birds. Breeding pairs started regular visits to the nest boxes and prepare the bedding with their regurgitated pellets which described the evidence of a breeding season associated with increased weekly prey uptake (Durant et al, 2010). Each female laid a single egg every one to three days to a total of four to eight eggs.…”