Nest defence behavioural reaction norms: testing life-history and parental investment theory predictions

Abstract

Predation is the primary source of reproductive failure in many avian taxa and nest defence behaviour against predators is hence an important aspect of parental investment. Nest defence is a complex trait that might consistently differ among individuals (personality), while simultaneously vary within individuals (plasticity) according to the reproductive value of the offspring. Both complementary aspects of individual variation can influence fitness, but the causality of links with reproductive success remains poorly understood. We repeatedly tested free-living female great tits ( Parus major ) for nest defence (hissing) behaviour across the nesting cycle, by presenting them with a model predator. Hissing behaviour was highly repeatable but, despite population-level plasticity, we found no support for individual differences in plasticity. Path analysis revealed that repeatable differences in hissing behaviour had no direct effect on nest success or fledgling number. However, our best supported path-model showed that more fiercely hissing females laid smaller clutches, with clutch size in turn positively influencing fledgling number, suggesting that females are most likely facing a trade-off between investment in nest defence and reproduction. Strong stabilizing selection for optimal plasticity, in combination with life-history trade-offs, might explain the high repeatability of nest defence and its link with reproductive success.

State dependence explains individual variation in nest defence behaviour in a long‐lived bird

“…Relatively few other studies have used a behavioural reaction norm approach to test for I × E in parental behaviours in general (Royle et al., 2014; Westneat et al., 2011) or, in nest defence behaviours in particular (Betini & Norris, 2012; Kontiainen et al., 2009; Thys et al, 2019). In line with our results, both in tree swallows Tachycineta bicolor (Betini & Norris, 2012) and Ural owls Strix uralensis (Kontiainen et al., 2009), bolder birds were found to be more plastic.…”

“…We used June day to model the seasonal gradient as opposed to nest stage (which is used in comparable studies e.g. Clermont et al, 2019; Thys et al, 2019), because this allowed us to take the whole dataset into account as we only have hatch dates for successful nests and lay dates were not determined. In general, there is limited variation in timing of hatch (average hatch day over all years (± SD ) = 32 ± 4 June days) and, therefore, we did not expect a marked difference in including season as June day or days until hatch for the subset of individuals for which hatch dates were known.…”

“…For example, many studies have reported, for a wide range of taxa, that individuals or pair members differ consistently in their nest or offspring defence behaviour over time or across contexts (e.g. mammals: Bubac et al., 2018, fish: Stein & Bell, 2015, birds: Burtka & Grindstaff, 2013; Clermont et al, 2019; Kontiainen et al., 2009; Patrick et al., 2013; Thys et al, 2019). Such consistent individual differences in behaviour (also referred to as ‘animal personality’) are intriguing because it implies that individual parents express limited plasticity in offspring care; that is, the range of plasticity an individual can display is smaller than the behavioural diversity that exists in the entire population (Sih et al., 2004).…”

The Effect of Pine Forest Structure on Bird-Mobbing Behavior: From Individual Response to Community Composition

“…Pettifor (1990) [41] did not find any difference in the response of common kestrels (Falco tinnunculus L.) to mobbing between seasons. No seasonality effect in responses to predator was also observed by Thys et al (2019) [38] in a free-living great tits (Parus major L.) in the surroundings of Wilrijk, Belgium. Shedd (1982Shedd ( , 1983 [42,43] showed different responses across months of two active mobbing species in deciduous woodland, one migrating (American robin Turdus migratorius) and one local (black-capped chickadee Parus atricapillus L.).…”

“…However, there is lack of information about the differences in reaction to mobbing between migrant, wintering, and all-year resident species. Previous studies examined bird responses to predators in the breeding season, but not between seasons, in various habitats such as alpine meadow [37], urban sites [38], and others (see reviews: [39,40]). Pettifor (1990) [41] did not find any difference in the response of common kestrels (Falco tinnunculus L.) to mobbing between seasons.…”