It is important to quantify vital rates of a species when designing conservation actions, especially in local populations of a species.
In this study, we used mark-recapture data on Northern Wheatears (Oenanthe oenanthe) collected over thirteen years and modelled annual survival and resighting probabilities for adult (male and female) and juvenile Wheatears in three study sites at Castricum, Den Helder, and the island of Texel, all in the Netherlands. We also wanted to compared survival and resighting probabilities between age classes and sexes, and check their variation between study sites.
The models for survival for all sites included time dependency, as we wanted to see the variation in survival over time. The models for resighting included the effect of time for Den Helder and Texel but did not include it for Castricum.
The results show that the population at Castricum had the lowest survival rates for both juveniles and adults. Survival rates at the Texel population were intermediate, and the population at Den Helder was the most stable in terms of survival. We also ran a model for the individuals of all the sites together, to show that site-specific analyses are indeed useful to see vital rate variations that may not show up in an overall analysis.
An additional model run for Den Helder with the interaction of time and state showed the effect of predation on female and juvenile survival. In another model, the effect of nest predation on adult females and juveniles was investigated for study site Den Helder, showing the difference in survival rates during those periods of predation by foxes or mustelids.
While it is clear now that the subpopulations of the Wheatear in the Netherlands have very different population dynamics, we suggest a future study that includes an Integrated Population Model, thereby estimating fecundity and immigration rates and uncovering the drivers of change for each subpopulation, and to what extent they push the populations.
Jaar van uitgave:
Radboud Universiteit Nijmegen
Type speciale uitgave: