Parent-offspring conflict over duration of parental care and its consequences in tawny owls Strix aluco

Abstract

In species defending territories, fitness of newly independent juveniles could depend on phenotypic quality or early access to vacant resources as a result of rapid dispersal. In the first case, parent-offspring conflict will arise when parents cease feeding maturing offspring while these still demand provisioning. In the latter case, the young should decide when to stop begging to search for vacant territories. I radio-tracked 72 juvenile tawny owls from independence to sexual maturity to investigate whether parents or offspring decided the timing of the onset of independence and compare effects of age versus date of independence on survival and reproductive status. Juvenile owls stopped begging when 90Á123 d old. This was synchronous within broods, independent of gender or age rank. Independence age of cross-fostered young varied across foster nests but was independent of hatching nest. After independence, young roosted in their parents' territory for 18 d on average before dispersal. This suggests that juvenile owls would rather extend dependency than disperse early. As predicted from this behaviour, age of independence had a positive influence on survival and reproductive status at maturity, whereas there were no effects of date of independence.

Melanin-based colour polymorphism signals aggressive personality in nest and territory defence in the tawny owl (Strix aluco)

“…Clutch sizes vary between one and eight eggs, which hatch between February and the end of May. Males deliver food to their offspring and partner (Sunde 2008;Sasvari et al 2009), while females distribute the prey items among the progeny. Nestlings leave the nest box even before they are able to fly, at an age of 25-30 days, but parents continue to feed and protect them until they are about 2 months old (Sunde 2008).…”

“…Males deliver food to their offspring and partner (Sunde 2008;Sasvari et al 2009), while females distribute the prey items among the progeny. Nestlings leave the nest box even before they are able to fly, at an age of 25-30 days, but parents continue to feed and protect them until they are about 2 months old (Sunde 2008). Because of their 5-10 % larger size and 20-25 % greater body mass (Glutz von Blotzheim 1987), females are also responsible for the majority of nest defence against predators (Wallin 1987), whereas in territorial disputes, males and females are equally active (Sunde and Bølstad 2004).…”

Sex- and melanic-specific variations in the oxidative status of adult tawny owls in response to manipulated reproductive effort

“…The female parent incubates the clutch for 28 days, and remains close to the nest to brood the hatchlings, distribute food among the progeny and protect the nest against predators (Da Silva et al, 2013), whereas the male parent hunts most prey items delivered to the nest. Offspring leave the nest at 25-30 days of age but are fed and protected by their parents until 90-120 days of age (Sunde, 2008). Hence, males and females are likely to differ in their reproductive constraints and, in turn, in the regulation of their oxidative balance in relation to brood food demand.…”

Family movements before independence influence natal dispersal in a territorial songbird

“…Such movements are likely to be restricted in year-round territorial species where parental territories are maintained throughout and beyond the period of postXedging care Nilsson 1990;Sunde 2008). In contrast, great tits defend exclusive territories at the onset of breeding but in the rest of the year roam more widely with a site-related dominance pattern (Drent 1983;Matthysen 1990).…”

“…While parents may control oVspring dispersal in several ways through maternal eVects on morphological or physiological phenotypes (Clobert et al 2001;de Fraipont et al 2000;Mondor et al 2005), conXicts of interest may also lead to behavioural conXicts concerning departure from the parental territory (Kokko and Lundberg 2001;Nilsson 1990;Sarno et al 2003;WolV 1993). In many territorial bird species, dispersal often follows closely upon the termination of parental provisioning (Clutton-Brock 1991;Sunde 2008). Nevertheless, while there is some evidence for parent-oVspring conXicts over the duration and extent of parental feeding (Arroyo et al 2002;Davies 1978;Leonard et al 1991) there is less evidence for parental control of dispersal.…”