Sex, personality and conspecific density influence natal dispersal with lifetime fitness consequences in urban and rural burrowing owls

Abstract

There is a growing need to understand how species respond to habitat changes and the potential key role played by natal dispersal in population dynamics, structure and gene flow. However, few studies have explored differences in this process between conspecifics living in natural habitats and those inhabiting landscapes highly transformed by humans, such as cities. Here, we investigate how individual traits and social characteristics can influence the natal dispersal decisions of burrowing owls (Athene cunicularia) living in urban and rural areas, as well as the consequences in terms of reproductive success and apparent survival. We found short dispersal movements among individuals, with differences between urban and rural birds (i.e., the former covering shorter distances than the latter), maybe because of the higher conspecific density of urban compared to rural areas. Moreover, we found that urban and rural females as well as bold individuals (i.e., individuals with shorter flight initiation distance) exhibited longer dispersal distances than their counterparts. These dispersal decisions have effects on individual fitness. Individuals traveling longer distances increased their reproductive prospects (productivity during the first breeding attempt, and long term productivity). However, the apparent survival of females decreased when they dispersed farther from their natal territory. Although further research is needed to properly understand the ecological and evolutionary consequences of dispersal patterns in transformed habitats, our results provide information about the drivers and the consequences of the restricted natal movements of this species, which may explain its population structuring through restricted gene flow between and within urban and rural areas.

Differences in adrenocortical responses between urban and rural burrowing owls: poorly-known underlying mechanisms and their implications for conservation

“…This results in an uneven occupation of territories by individuals with different tolerances to humans, which cannot be completely explained through habituation. Indeed, FID is highly repeatable throughout an individual’s adulthood ( Carrete and Tella, 2010 , 2013 ), and it is correlated with other behaviours such as exploration, anti-predator behaviour and dispersal within behavioural syndromes that differ between urban and rural birds ( Carrete and Tella, 2017 ; Luna et al , 2019a , 2019b ). Recent full-genome sequencing approaches performed in different burrowing owl populations (including those of our study area) reinforce the idea that cities were colonized a few decades ago by a small number of founders from the surrounding natural areas ( Mueller et al , 2018 ), with an enrichment of different genes related to personality, behavioural control, memory and cognitive/learning functions ( Mueller et al , 2020 ).…”

Urban life promotes delayed dispersal and family living in a non-social bird species

“…The mean lifespan of burrowing owls is relatively short, ranging between 1.3 and 2.9 yrs 57 , 101 . Individuals typically recruit into the breeding population during their first year of life in September–October 56 . Our long-term monitoring (from 2006 to 2018) suggests that there are no floaters or, at least, that this strategy is extremely rare.…”

“…The city is immediately surrounded by large rural expanses of natural and transformed grasslands, without barriers that may constrain the movements of owls between habitats 101 . Moreover, as owls can excavate their burrows, their dispersal is not expected to be constrained by territory availability 36 , 56 .…”

“…Only 340 individuals out of the 1,579 birds ringed as chicks were resighted during their first breeding attempt, most of them (318 individuals) forming breeding pairs (one male and one female) at different distances to their natal areas 56 . However, ca.…”

“…Previous research has shown that breeding densities and productivity of this species are notably higher in the city than in their adjacent rural areas due to predation release 48 . This fact, in addition to the differential behavioural profiles of urban compared to rural birds 41 , 52 , 60 , has promoted differences in the natal and breeding dispersal patterns of both groups of birds, with urban individuals being less prone to disperse or dispersing at shorter distances than rural ones 55 , 56 . However, it is unknown whether urban life and their associated changes in an individual’s natal dispersal pattern could also affect the decision of some to remain in their natal nests until their second year of life, delaying dispersal and leading to the formation of unusual family units.…”