Who are we sampling? Apparent survival differs between methods in a secretive species

Abstract

Survival is a fundamental parameter in population dynamics with increasing importance in the management and conservation strategies of wildlife populations. Survival probability in vertebrates is usually estimated by live-encounter data obtained by means of physical markÁcaptureÁrecapture protocols. Non-invasive acoustic marking relying on individual-specific features of signals has been alternatively applied as a marking technique, especially in secretive species. Nevertheless, to date no research has compared survival rate estimates obtained by acoustic and physical marking. We estimated half-yearly and annual survival and recapture rates of a secretive and threatened passerine, the Dupont's lark Chersophilus duponti, using two separate live-encounter data sets of males collected simultaneously by physical and acoustic marking in the same study area. The separate analysis of both methods led to different model structures, since transient individuals had to be accounted for in the acoustic marking but not in the physical marking data set. Furthermore, while reencounter probabilities did not differ between methods, survival estimates employing physical marking were lower than those obtained acoustically, especially between the postbreeding and the breeding period when the apparent survival of colour-banded birds was twice as low as for acoustic marking. The combination of marking methods suggested the existence of different subsets of individuals differentially sampled within the population: whereas colour-banded males seemed to represent the territorial fraction of the population, both resident and floater individuals were probably detected by acoustic marking. Using traditional markÁrecapture methods exclusively could have misled our estimates of survival rates, potentially affecting prospective predictions of population dynamics. Acoustic marking has been poorly applied in markÁrecapture studies, but might be a powerful complement to obtain accurate estimates of fundamental demographic parameters such as survival and dispersal.

An island paradigm on the mainland: host population fragmentation impairs the community of avian pathogens

“…All fragments of a suitable habitat separated by a distance of less than 1 km from the nearest neighbour fragment were assigned to the same population (figure 1), based on spatial analyses of connectivity and the species' behaviour [18]. Dupont's lark population sizes were calculated as the number of occupied territories through territory mapping of males aided by its acoustic identification and observations of individually colour-banded birds [17]. Dupont's lark breeding densities were determined as (i) the number of occupied territories divided by patch size, and (ii) the mean distance between the nearest singing male neighbours [16,18].…”

“…Remarkably, our results resemble those obtained by Lindström et al [33], which showed a consistent increase in three parasites (two species of feather mites and avian pox virus) in island populations of Darwin's finches with increasing island size. Our host study model species has a very low dispersal rate [16,17], as well as disrupted culture transmission at small spatial scales [34]. All of these factors suggest an unusual scenario of island effects in a mainland vertebrate.…”

“…small patch sizes, barriers of hostile habitat hampering dispersal). Indeed, extensive capture-mark -recapture studies revealed extraordinarily few movements among these populations, although more than half of them are separated by only 1-3 km [16,17]. Furthermore, we took into account possible spill-over effects [1] from alternative hosts (i.e.…”

Restricted gene flow and genetic drift in recently fragmented populations of an endangered steppe bird

“…Although Dupont's lark is currently the subject of several conservation research studies (Garza et al, 2005;Laiolo and Tella, 2005, 2006a,b, 2007Seoane et al, 2006;Suárez et al, 2009;Vögeli et al, 2008Vögeli et al, , 2010Vögeli et al, , 2011a, genetic processes occurring within and among populations remain largely unknown. A recent phylogenetic study showed that the Spanish populations are isolated from the Moroccan ones (García et al, 2008).…”

Mimicry as a novel pathway linking biodiversity functions and individual behavioural performances

“…On the other hand, it should be stressed that bird local populations are rarely isolated, and natal and breeding dispersal permits females to move and come into contact with different social environments [64]. Lark females dispersing in winter or early spring [65,66], for instance, may experience the songs of males from different local neighbourhoods and eventually choose their breeding territories on the basis of song cues at the transect or site scale [67,68].…”