Integrated population model reveals that kestrels breeding in nest boxes operate as a source population

Abstract

The identification of the source-sink status of a population is critical for the establishment of conservation plans and enacting smart management decisions. We developed an integrated population model to formally assess the source status of a kestrel Falco tinnunculus population breeding in nest boxes in Switzerland. We estimated juvenile and adult survival, reproduction and net dispersal (emigration/immigration) by jointly analyzing capture-recapture, dead recovery, breeding monitoring and population survey data. We also investigated the role of nest boxes on kestrel demography and assessed the contributions of vital rates to realized population growth rates. The results indicate that the kestrel population breeding in nest boxes has acted as a source over the 15 years of the study duration. A quantitative approach suggests that a substantial number of individuals have emigrated annually from this population likely affecting the population dynamics outside the management area. Variation in fecundity explained 34% of the temporal variability of the population growth rate. Moreover, a literature review suggests that kestrel pairs produce on average 1.4 chicks more per breeding attempt in nest boxes compared to natural open nests. Together, these findings suggest that fecundity was an important driver for the dynamics of this population and that nest boxes have contributed to its raise. Nest boxes are regularly used as an efficient tool for conservation management. We suggest that such a conservation action can result in the establishment of a source population being beneficial for populations both inside and outside the managed area.

Consequences of violating assumptions of integrated population models on parameter estimates

“…To maximize the generality of our results, we included in our simulations two different life-histories and simulated data for 15 years, corresponding to a typical duration of IPM studies, which is often between 10 and years (20 years: Tenan et al 2017, 16 years: Plard et al 2020, 15 years: Lieury et al 2015Hatter et al 2017;Fay et al 2019, 14 years: Duarte et al 2016, 12 years: Brommer et al 2017, 11 years: Cleasby et al 2017, even if some studies last longer (22 years: Tempel et al 2014, 30 years: Margalida et al 2020 or shorter (7 years, Duarte et al 2017). We chose to simulate a relative large number of individuals (300 individuals) compared to population sizes of empirical IPMs which was often between 20 and 300 individuals (in the articles cited above).…”

Demography of a widespread raptor across disparate regions

“…For example, densitydependent processes are important for the dynamics of Mauritius Falco punctatus (Nicoll et al 2003) and Lesser Kestrels Falco naumanni (Di Maggio et al 2016). Moreover, Hiraldo et al (1996) showed that population growth of Lesser Kestrels in southern Spain was most sensitive to changes in adult survival, whereas fecundity is a prominent driver of population change in a population of Eurasian Kestrels Falco tinnunculus in Switzerland (Fay et al 2019). Given the similar life-histories of kestrel species, inference from the population dynamics of other kestrels might inform the conservation of the American Kestrel.…”

Why we should care about movements: Using spatially explicit integrated population models to assess habitat source–sink dynamics

“…These are estimated independently for each year. One interpretation of them is that they represent, as the name suggests, the net numbers of immigrants in Short and Tall habitats (see also Fay et al., 2019 for a similar formulation). This may be seen by rewriting the population model above as (again omitting demographic stochasticity for clarity):Thus, it is the difference between the number of breeders in a given habitat inside the local population (estimated from count data) and the projected total number of breeders in this habitat in the total population originating from the local population in the previous year.…”

“…This is true at the scale of the habitat‐specific subpopulations (exchanges between sources and sinks within the population) and also at larger spatial scales (movements between populations). To date, few studies have accounted for permanent emigration when estimating the source or sink status of single study populations (but see Fay et al., 2019; Weegman et al., 2016). Moreover, few studies have considered movements between habitat types or subpopulations in order to better estimate the demographic contribution of local habitats to the overall studied population (but see Paquet et al., 2019; Pasinelli et al., 2011; Seward et al., 2019) and none of these studies accounted for permanent emigration from the study area (Furrer & Pasinelli, 2016).…”