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Staging to join non-kin groups in a classical cooperative breeder, the Florida scrub-jay

Citation

Suh, Young Ha; Bowman, Reed; Fitzpatrick, John (2022), Staging to join non-kin groups in a classical cooperative breeder, the Florida scrub-jay, Dryad, Dataset, https://doi.org/10.5061/dryad.dz08kprzw

Abstract

1. Why unrelated members form groups in animal societies remains a pertinent topic in evolutionary biology because benefits for group members often are not obvious. We studied subordinates that disperse to join unrelated social groups in the Florida scrub-jay Aphelocoma coerulescens, a cooperative breeding species mainly composed of kin-based groups. 2. We evaluated potential adaptive benefits of dispersing to become an unrelated helper (staging) versus remaining home and dispersing only to pair and breed (direct dispersal) to understand why non-kin-based groups form. 3. Using 35 years of demographic data, we quantified life history aspects of staging individuals and tested associations between social and ecological factors on the natal and staging territories. We compared fitness outcomes between dispersal strategies by analyzing survival, breeding recruitment, and direct reproductive output. We tested for sexual asymmetry potentially driven by differences in territory acquisition patterns and female-biased dispersal for this species. 4. Of birds that reached one-year-old, 28% staged at a non-natal territory before breeding or disappearing. Staging dispersers departed at younger ages and moved greater distances than direct dispersers. When looking at proximate factors on the natal territory associated with staging, males left groups with many same-sex helpers, while females often left when their father disappeared. For both sexes, staging individuals more likely came from high-quality territories and joined groups with fewer same-sex helpers than in their natal group. While staging and direct dispersers did not differ in survival or likelihood of becoming a breeder, staging males became breeders later and had lower lifetime reproductive success than direct dispersers. 5. In Florida scrub-jays, staging appears to be an alternative strategy for female helpers, but a best-of-a-bad-situation for males. This sexual asymmetry is consistent with males having more options than females to achieve higher reproductive success by breeding near home. Tradeoffs in cost-benefits of departing natal territory and joining unrelated groups as a helper seem to best explain alternative dispersal patterns, with optimal social queues primarily driving the benefits. This research highlights plasticity in dispersal behavior in response to social and environmental conditions and offers new perspective in our understanding of non-kin-based social groups.

Methods

We used data collected continuously over 35 years from a color-banded population of Florida scrub-jays at Archbold Biological Station in central Florida (27.10°N, 81.21°W). As part of this long-term research, monthly censuses are conducted to document resident territory, group composition, survival, and dispersal. All nests are located each year, providing detailed records of reproductive success (Fitzpatrick & Bowman, 2016; Woolfenden & Fitzpatrick, 1984). All territory boundaries are mapped early in each breeding season, and these are overlaid on habitat and fire maps annually available at Archbold Biological Station (Abrahamson et al., 1984). Using these data, we calculated the amount of oak scrub habitat available and amount of scrub habitat that was burned in the past 10 years on the natal territory to represent measures of territory quality (Fitzpatrick & Bowman, 2016; Mumme et al., 2015).

Usage Notes

Contact corresponding author for R script. 

Funding

National Science Foundation, Award: BSR-8705443

National Science Foundation, Award: BSR-8996276

National Science Foundation, Award: BSR-9021902

National Science Foundation, Award: DEB97-07622

U.S. Fish and Wildlife Service