Sex roles during post-fledging care in birds: female Tengmalm’s Owls contribute little to food provisioning

Abstract

Post-fledging care constitutes a large proportion of the total costs of parental care in many bird species. Despite being recognized as of critical importance to the survival of the offspring and their recruitment into the breeding population, post-fledging care, including the relative contribution by male and female parents, is understudied. In this study, we quantified food provisioning (prey deliveries) by male and female Tengmalm's Owl (Aegolius funereus) parents to their offspring both in the nestling and the post-fledging stages, in years of differing natural prey abundance. Parents and at least one offspring in 26 families were fitted with radio-transmitters. Male parents exhibited higher delivery rates than did females throughout the late nestling and post-fledging stages, but the intersexual difference was smaller in broods that were not deserted by the female at any stage. The female deserted her mate and offspring at some stage in 63% of the broods. Overall, deserted males delivered more prey to their offspring than did non-deserted males. Delivery rates were generally higher post-fledging. Prey delivery rates differed among years, and were highest in low vole years (probably because of smaller prey items), intermediate in peak vole years, and lowest in years of vole increase. Prey delivery rates increased with increasing brood size for both sexes, but the response was stronger in females. We suggest that female Tengmalm's Owls contribute less than males because they are in a position to decide on their level of provisioning effort first, and because of the potential for re-mating after deserting the first brood. ZusammenfassungGeschlechterrollen bei der Fü rsorge fü r Flü gglinge: Weibliche Raufußkäuze tragen wenig zur Futterversorgung bei Die Fürsorge für Flügglinge macht bei vielen Vogelarten einen großen Anteil der Gesamtkosten der Brutpflege aus. Obwohl bekannt ist, dass die Fürsorge für Flügglinge von entscheidender Bedeutung für das Ü berleben der Nachkommen und ihre Rekrutierung in die Brutpopulation ist, ist dieser Aspekt der Brutpflege, einschließlich des relativen Beitrags von Männchen und Weibchen, nicht gut untersucht. In dieser Studie haben wir in Jahren mit unterschiedlicher natürlicher Beuteabundanz quantifiziert, wie männliche und weibliche Raufußkäuze (Aegolius funereus) ihre Nachkommen mit Futter versorgten, sowohl im Nestlingsstadium als auch nach dem Ausfliegen. Die Elternvögel und mindestens ein Jungvogel aus 26 Familien wurden mit Radiosendern ausgestattet. Männchen wiesen während des späten Nestlingsstadiums und nach dem Ausfliegen höhere Fütterraten auf als Weibchen, aber der Unterschied zwischen den Geschlechtern war geringer in Bruten, die nicht zu irgendeinem Zeitpunkt vom Weibchen verlassen wurden. Das Weibchen verließ irgendwann Communicated by T. Friedl. Electronic supplementary materialThe online version of this article (seinen Partner und seine Nachkommen in 63% der Bruten. Insgesamt brachten verlassene Männchen ihren Nachkommen mehr Beute als nicht verlassene. Die Fütt...

A few long versus many short foraging trips: different foraging strategies of lesser kestrel sexes during breeding

“…2). Females performed a higher number of foraging trips and traveled larger distances as chick age increases, probably because the provisioning activity of males is insufficient and females help them to deliver food to the nest, as has been described in other species [20, 25, 74–76]. On the other hand, kestrel males drastically decrease colony attendance from the incubation to the nestling period, which is to be expected because of the elevated energy demand associated with feeding the chicks.…”

Differential Movement Patterns of Juvenile Tengmalms Owls (Aegolius funereus) during the Post-Fledging Dependence Period in Two Years with Contrasting Prey Abundance

“…Hatching occurs at approximately two-day intervals [37]. The young stay in the nest for 28–32 days after hatching [38]–[40], thus fledging at different times, and reach independence 5–7 weeks after fledging [38], [41]–[43]. The great majority of prey brought to the young throughout the late nestling and PFDP in this particular species, is delivered by the male [42]–[44].…”

“…We expected that after all individuals fledged from their nest box they would follow the provider, which would be most likely the male [41]–[43], and gradually increase the distance from the nest box. Because the provider would have to move farther to find prey when these are scarce, we would expect the distance between the young and the nest box to be longer and home ranges to be larger when prey abundance is lower.…”

“…Whatever the availability of prey in any season, an effect would be expected in relation to increasing brood size because such broods will need more food items than smaller broods and the provider will also need to forage over a larger area. Such movements may be further exacerbated due to the absence of the female and her help in feeding the young during the PFDP [41]–[43].…”

Effect of male provisioning on the parental behavior of female Boreal Owls Aegolius funereus

“…After the brooding period, females may either help males in providing food for the young or desert them (Eldegard and Sonerud 2009;Zárybnická 2009a;Korpimäki et al 2011). When a female deserts, its mate compensates for the absent female's contribution and continues to care for the nestlings (Korpimäki 1981;Zárybnická 2009a;Eldegard and Sonerud 2012) and fledglings until they become independent (6 to 7 weeks after fledging, Eldegard and Sonerud 2012). Males can be polygynous and simultaneously pair with two or even three females (Carlsson et al 1987;Carlsson and Hörnfeldt 1989;Korpimäki 1991).…”