Natal dispersal does not entail survival costs but is linked to breeding dispersal in a migratory shorebird, the southern dunlin Calidris alpina schinzii

The costs and benefits of dispersal are often assessed by comparing
fitness between dispersing and non-dispersing individuals. Importantly,
individuals that disperse between their natal and first breeding site may
subsequently be more likely to disperse between breeding sites compared to
those that remained philopatric to their natal site. Such
within-individual consistency in dispersal behaviour can bias local
survival estimation, and thus the survival comparison between dispersing
and non-dispersing individuals, if breeding dispersal leads to permanent
emigration from the study area. We examined whether adult survival
correlates with natal dispersal in a migratory shorebird, the southern
dunlin (Calidris alpina schinzii), in two isolated patchy populations
where permanent emigration is expected to be extremely rare. To assess
whether local adult survival could be biased by non-random breeding
dispersal, we analysed between-patch breeding dispersal probability and
quantified within-individual consistency in dispersal. Among females,
natal dispersers were more likely to disperse again as adults compared to
non-dispersers, while no difference was observed in males which were
always highly site faithful. Yet, adult survival did not differ between
natal dispersing and non-dispersing individuals in either sex. Breeding
dispersal probability was higher in failed compared to successful
breeders. Breeding dispersal often resulted in dispersal back to the natal
patch, i.e. delayed natal philopatry. Our results suggest no survival
costs of dispersal after first reproduction. Despite individual
consistency, survival estimates of dispersing individuals were not biased
because nearly all available breeding habitat was covered. We show that
consistency in dispersal can occur even in site faithful species like the
southern dunlin. Studies of the effects of dispersal on survival should
therefore account for within-individual consistency in dispersal if not
all available breeding habitat is monitored in open populations. In
particular, delayed natal philopatry may lead to biased local survival
estimates for immigrants when compared with philopatric individuals.