Natal dispersers pay a lifetime cost to increased reproductive effort in a wild bird population

Abstract

Natal dispersal is assumed to be costly. Such costs can be difficult to detect, and fitness consequences of dispersal are therefore poorly known. Because of lower phenotypic quality and/or familiarity with the environment, natal dispersers may be less buffered against a sudden increase in reproductive effort. Consequently, reproductive costs associated with natal dispersal may mostly be detected in harsh breeding conditions. We tested this prediction by comparing lifetime reproductive success between natal dispersers and non-dispersers in a patchy population of collared flycatchers ( Ficedula albicollis ) when they reared either a non-manipulated brood or an experimentally increased or decreased brood. Natal dispersers achieved lower lifetime reproductive success than non-dispersers only under more stressful breeding conditions (i.e. when brood size was experimentally increased). This was mostly due to a lower number of recruits produced in the year of the increase. Our results suggest a cost associated with natal dispersal paid immediately after an increase in reproductive effort and not subsequently compensated for through increased survival or future offspring recruitment. Natal dispersers adjusted their breeding investment when reproductive effort is as predicted but seemed unable to efficiently face a sudden increase in effort, which could affect the influence of environmental predictability on dispersal evolution.

The new kid on the block: immigrant males win big whereas females pay fitness cost after dispersal

“…Our results are not consistent with earlier studies (Gienapp & Meril€ a 2011;Waser et al 2013;Germain et al 2017) where dispersers did not incur fitness costs after recruitment. In the one earlier mammalian study (Waser et al 2013), they did not detect long-term fitness benefits for either sex likely because kangaroo rats do not show sex-biased dispersal.…”

“…Because dispersal theory does not hypothesise dispersal costs and benefits to be intergenerational, we do not expect there to be intergenerational effects. Earlier studies (Waser et al ; Germain et al ) reported results consistent with immigrants making the best of a bad lot, but found no sex differences.…”

Selection against immigrants in wild seabird populations

“…Immigrants had generally lower fitness than residents. This is in line with the results from a previous study on fish (Peterson et al, 2014) and some studies of birds (Verhulst and Van Eck, 1996;Bensch et al, 1998) and mammals (Martinig et al, 2020), but is not consistent with others (birds: Gienapp and Meril€ a, 2011;Germain et al, 2017;mammals: Waser et al, 2013). In another long-lived species, the Audouin's gull Larus audouinii, Oro et al (2011) compared fitness components among residents and immigrants and found differences in recapture probabilities, suggesting higher site-tenacity for residents than for immigrants, but similar survival and recruitment.…”

House sparrows’ (Passer domesticus) behaviour in a novel environment is modulated by social context and familiarity in a sex-specific manner

“…Behavioural responses to novel environments (such as exploratory behaviour and neophobia) are considered critical targets of selective pressures [ 1 – 3 ]. While animals exposed to unfamiliar environments generally perceive them as less predictable and more dangerous than familiar places and situations [ 4 – 6 ], they are often forced to explore, disperse and colonise new areas [ 7 , 8 ]. However, exploratory traits are often investigated using animals in an individual context, while the presence of conspecifics can modulate the expression of behavioural responses, for example through social facilitation (change of rate of certain behavioural responses, sensu [ 9 ]).…”