Differences in incubation behaviour and niche separation of two competing flycatcher species

Tuuli-Marjaana Koski,Murielle Ålund,Päivi M Sirkiä,S Eryn Mcfarlane,Anna Qvarnström

doi:10.1007/s00265-020-02883-4

Abstract

Food availability sets the stage for incubation behaviour of a female bird and thereby indirectly determines the nest temperature, which in turn affects development and metabolism of avian embryos. Changes in development and metabolism in turn are known to influence offspring’s ability to adjust to environmental changes later in life. However, few studies have investigated the role of interspecific differences in incubation behaviour in relation to niche separation between competing sibling species. We studied the effects of habitat quality (in terms of caterpillar availability) on incubation behaviour of two ecologically similar and closely related species, collared and pied flycatchers (Ficedula albicollis and F. hypoleuca), in their hybrid zone on the island of Öland, Sweden. Even though both species prefer caterpillar-rich deciduous forests as nesting sites, collared flycatchers, whose nestlings have higher energetic demands, are able to nest only in deciduous forests, whereas pied flycatchers have more flexible habitat requirements. Overall, higher food availability was associated with increased nest attendance, higher incubation temperature and a lower number of foraging trips across species. In addition, collared flycatchers had more frequent and shorter foraging trips across habitat types, allocated more heat to eggs and therefore maintained higher nest temperatures compared to pied flycatchers. We argue that the higher heat allocation or the need to maintain a higher nest temperature for embryo development may constrain collared flycatchers to focus on relatively more profitable prey. Our results highlight the importance of considering incubation behaviour in the context of understanding species differences in niche use.Significance statementNiche separation plays an important role in mitigating effects of competition between closely related species. Whether species differences in incubation behaviour relate to differences in niche use remains unknown. We compared incubation behaviour of two sympatric flycatcher species that differ in sensitivity to food availability. The competitively more dominant and larger species, the collared flycatcher, whose nestlings are more sensitive to food shortages, made more frequent foraging trips but allocated more heat to eggs, leading to higher nest temperature despite lower nest attendance, compared to pied flycatchers. These interspecific differences may be a result of differences in embryo sensitivity or female physiology and contribute to the niche separation between the species, which in turn can facilitate coexistence.

Highlights

Incubation is an important part of parental investment for birds, because by altering the egg thermal environment, the parent influences the hatching success and timing and the later viability and competitive ability of the offspring by affecting, for example, their metabolism and phenotype (Hepp et al 2006; Olson et al 2006; Ardia and Clotfelter 2007; Wada et al 2015; Nord and Nilsson 2011, 2016; Mueller et al 2019)
The competitively more dominant and larger species, the collared flycatcher, whose nestlings are more sensitive to food shortages, made more frequent foraging trips but allocated more heat to eggs, leading to higher nest temperature despite lower nest attendance, compared to pied flycatchers
Among breeding pairs sampled in this study, the average habitat quality was similar in territories occupied by collared and pied flycatchers

Summary

Introduction

Incubation is an important part of parental investment for birds, because by altering the egg thermal environment, the parent influences the hatching success and timing and the later viability and competitive ability of the offspring by affecting, for example, their metabolism and phenotype (Hepp et al 2006; Olson et al 2006; Ardia and Clotfelter 2007; Wada et al 2015; Nord and Nilsson 2011, 2016; Mueller et al 2019). In high-quality territories, birds are more likely able to take fewer or shorter off-bouts, i.e. foraging trips out of the nests, and have longer on-bouts, i.e. nest-attendance periods between off-bouts (Drent et al 1985; Eikenaar et al 2003; Rastogi et al 2006; Ardia and Clotfelter 2007; Amininasab et al 2016; Vafidis et al 2018) This in turn should affect hatching success, offspring quality and/or the likelihood for the offspring surviving to adulthood due to more constant or higher incubation temperatures, and/ or shorter incubation periods (number of days incubated before hatching), (Ardia and Clotfelter 2007; Nord and Nilsson 2011, 2016; Mueller et al 2019)

Methods

Results

Conclusion