Flight initiation distances of birds

Habitat destruction and fragmentation increasingly brings humans into
close proximity with wildlife, particularly in urban contexts. Animals
respond to humans using nuanced anti-predator responses, especially
escape, with responses influenced by behavioural and life history traits,
the nature of the risk, and aspects of the surrounding environment.
Although many studies examine associations between broad-scale habitat
characteristics (i.e., habitat type) and escape response, few investigate
the influence of fine-scale aspects of the local habitat within which
escape occurs. We test the ‘habitat connectivity hypothesis’ which
suggests that, given the higher cost of escape within less connected
habitats (due to the lack of protective cover), woodland birds should
delay escape (tolerate more risk) than when in more connected habitat. We
analyse flight-initiation distances (FIDs) of five species of woodland
birds in urban Melbourne, south-eastern Australia. A negative effect of
habitat connectivity (the proportion of the escape route with
shrubs/trees/perchable infrastructure) on distance fled was evident for
all study species, suggesting a higher cost of escape associated with
lower connectivity. FID did not vary with connectivity at the location at
which escape was initiated (four species), apart from a positive effect of
habitat connectivity on FID for Noisy Miner Manorina melanocephala. We
provide some support for two predictions of the ‘habitat connectivity
hypothesis’ in at least some taxa, and conclude it warrants further
investigation across a broader range of taxa inhabiting contrasting
landscapes. Increasing habitat connectivity within urban landscapes may
reduce escape stress experienced by urban birds.