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

Markéta Zárybnická,Jiří Vojar

doi:10.1186/1810-522x-52-36

Abstract

Background: Sex-specific parental roles of most raptors allow mates to cooperate during breeding; while females incubate and brood, males provide food. If one partner fails in its parental duties, however, sex-specific parental roles can limit the ability of each sex to carry out the role normally performed by its partner. We observed the effect of male food provisioning on female parental care in Boreal Owls Aegolius funereus using cameras at 12 nests in western Finland in 2005. We compared the parental care of eight females in nests with a high male feeding rate (successful nests) with that of the females in four nests with a low or zero male feeding rate (failed nests). Results: Females brooded more intensively in nests where males provided sufficient food for the family. These females continually stayed with the young until the late brooding stage (18 days after hatching). After completing the brooding period (21 days after hatching), they either no longer visited their nests or began to provide food to their young together with males. Females exposed to a low or zero male feeding rate left their young for long periods without brooding during the early brooding stage (8 days after hatching) and provisioned nestlings at a mean rate of 0.6 ± 0.8 prey items/night. As a consequence, all of these nesting attempts failed. One female that was widowed 21 days after hatching stopped brooding and began food provisioning alone, but only one of six young successfully left the nest. Body masses of females in successful and unsuccessful nests were similar, indicating that females in nests with insufficient provisioning did not markedly suffer from a lack of food. Conclusions: Female Boreal Owls adjusted their parental care based on the level of parental effort of their mates and the nesting phase. The nesting attempts, in which males did not provide enough food for the family during the early brooding stage, failed. We concluded that bi-parental care in northern populations of Boreal Owls is essential until brooding is completed.

Highlights

Sex-specific parental roles of most raptors allow mates to cooperate during breeding; while females incubate and brood, males provide food
Bird species with sex roles that are not strictly specialized and with similar body sizes for both sexes have shown that one-parent care may occur early in the nestling period, and either both parents or at least one parent is able to compensate for a task of the missing partner (e.g., Snow Buntings Plectrophenax nivalis, Lyon et al 1987; Spanish Sparrow Passer hispaniolensis, Marques 2004; Northern Flicker Colaptes auratus, Wiebe 2005, 2010; Rock Sparrow Petronia petronia, Griggio and Pilastro 2007; Penduline Tit Remiz pendulinus, van Dijk et al 2007)
Our findings indicate that the stage of the nesting phase can influence whether or not a Boreal Owl female provides single-parent care

Summary

Introduction

Sex-specific parental roles of most raptors allow mates to cooperate during breeding; while females incubate and brood, males provide food. Bi-parental care occurs in most monogamous bird species with altricial or semi-precocial young (Lack 1968; Clutton-Brock 1991; Székely et al 2007) Such birds exhibit more or less divided parental duties during nesting; on the one hand, there are species in which both males and females cooperate in incubation, brooding, food provisioning, or nest defense (e.g., waders, gulls, auks, pigeons, and passerines), and on the other hand, there are species in which males and females have strictly divided parental task; females usually incubate and brood, while males provide most food for the young and female (e.g., most diurnal raptors and owls). There is no solid information as to under what conditions a raptor or owl parent would substitute the duties of its mate and how the contribution of one mate affects the parental effort of the other mate

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