A genetic approach to estimating natal dispersal distances and self-recruitment in resident rainforest birds
Natal dispersal is a fundamental component of the ecology and evolutionary history of birds, yet is often prohibitively difficult to study. We characterized natal dispersal for the first time in a bird using molecular genetic parentage analyses in a tropical rainforest understory species, the chestnut-backed antbird (Thamnophilidae: Myrmeciza exsul). Median natal dispersal distance was similar to 800 m (mean = 931 +/- 84 (SE) m, n = 48), with similar to 90% of all distances < 1500 m. We found no evidence of sex-biased dispersal. An index of self-recruitment (i.e. individuals establishing a territory within the population of origin) was higher in sites largely or entirely surrounded by non-forest, suggesting birds are reluctant to disperse out of preferred forest habitat. Via simulations, we confirmed that the genetic data had sufficient resolution to correctly identify parent-offspring dyads, but lacked resolution to identify other relationships (full-sib and half-sib) with confidence. Chestnut-backed antbirds have measurable self-recruitment rates caused by short natal dispersal distances, and self-recruitment may be amplified by reluctance to disperse out of sites bordered by non-forest. Some tropical forest understory birds have naturally short dispersal distances, and our results have implications for understanding how species will be affected by fragmented landscapes and for the design of reserves.