Joint care can outweigh costs of nonkin competition in communal breeders

Abstract

Parents who raise their nestling in a communal nest alongside the nestling of other parents can reduce costly competition between offspring by providing more food. In the Seychelles warbler, we show that nestlings raised with a sibling have lower mass and survival than those raised alone, whereas nestlings raised with a nonsibling do not suffer these costs. Our results suggest that increased food provisioning can reduce competition among nonsiblings and facilitate the evolution of joint-nesting.

Habitat Saturation Results in Joint-Nesting Female Coalitions in a Social Bird

“…As cavity nesters, acorn woodpeckers are also restricted by the size of the nest cavity, a constraint that potentially affects clutch size (Slagsvold 1989;Wiebe et al 2006). Thus, environmental and ecological factors, combined with physiological limitations, may constrain the number of nestlings produced by females with significant costs for females breeding in a coalition (Bebbington et al 2017).…”

“…Female coalitions can produce more offspring than singleton females, but this is offset by limited food resources, physiological constraints on brooding and incubation due to relative egg size, and added provisioning requirements for the augmented number of young (Bebbington et al 2017) that results in decreasing per capita reproductive output for each additional breeder female (Vehrencamp 2000). Females thus incur a significant loss in direct fitness when joint nesting compared to independent breeding.…”

“…Intraspecific brood parasitism is considered a potentially important behavioral precursor and evolutionary pathway to joint nesting among females (McRae 1996b). If the breeding female is not able to evict the parasitizing female, the latter may be permitted to provision the combined offspring (Bebbington et al 2017). If the parasitizing female is related to the breeding female, however, inclusive fitness benefits may offset any direct fitness losses (Yom-Tov 1980;McRae 1996b;Zink and Lyon 2016).…”

Telomere attrition: metabolic regulation and signalling function?

“…Several testable predictions arise from the metabolic telomere attrition hypothesis (table 1): (1) TL shortening is expected whenever organisms face major energetic challenges that are perceived by the cell (via TOR) and induce specific metabolic adjustments like a promotion of catabolic over anabolic processes to re-establish energy balance. Thus, TL attrition is likely to occur in life-history stages characterized by high metabolic demands, like growth [138], migration and reproduction [137], during challenging environmental conditions [135], and in the wake of energetically costly processes like immune activation [50], high work load [133], antagonistic challenges [139] or poor availability of resources [140]. (2) During times of energy shortages, organismal changes should occur (and will have to be studied in detail) at two levels: (i) in the physiological mechanisms that link energetic state, cell metabolism and TL dynamics like mitochondrial functioning, phosphorylation status of target kinases or gene expression; (ii) in the relationship between TL attrition and the resulting condition of the organism.…”

“…Repeated assessments of TL lengths and metabolic processes in individuals of different body condition experiencing demanding conditions are needed to test this prediction [4]. Ideally, such tests should be carried out in natural populations, which are exposed more frequently to settings that require resource trade-offs [133,135,[137][138][139][140] than populations living in sheltered laboratory conditions. (3) TL dynamics will be influenced by a range of metabolic regulators, including GCs, thyroid and sex hormones, insulin, energy-sensing kinases and proteins.…”