Ecological and social effects on reproduction and local recruitment in the red-backed shrike

Abstract

Numerous hypotheses have been proposed to explain variation in reproductive performance and local recruitment of animals. While most studies have examined the influence of one or a few social and ecological factors on fitness traits, comprehensive analyses jointly testing the relative importance of each of many factors are rare. We investigated how a multitude of environmental and social conditions simultaneously affected reproductive performance and local recruitment of the red-backed shrike Lanius collurio (L.). Specifically, we tested hypotheses relating to timing of breeding, parental quality, nest predation, nest site selection, territory quality, intraspecific density and weather. Using model selection procedures, predictions of each hypothesis were first analysed separately, before a full model was constructed including variables selected in the single-hypothesis tests. From 1988 to 1992, 50% of 332 first clutches produced at least one fledgling, while 38.7% of 111 replacement clutches were successful. Timing of breeding, nest site selection, predation pressure, territory quality and intraspecific density influenced nest success in the single-hypothesis tests. The full model revealed that nest success was negatively associated with laying date, intraspecific density, and year, while nest success increased with nest concealment. Number of fledglings per successful nest was only influenced by nest concealment: better-camouflaged nests produced more fledglings. Probability of local recruitment was related to timing of breeding, parental quality and territory quality in the single-hypothesis tests. The full models confirmed the important role of territory quality for recruitment probability. Our results suggest that reproductive performance, and particularly nest success, of the red-backed shrike is primarily affected by timing of breeding, nest site selection, and intraspecific density. This study highlights the importance of considering many factors at the same time, when trying to evaluate their relative contributions to fitness and life history evolution.

Possible causes and consequences of philopatry and breeding dispersal in red-backed shrikes Lanius collurio

“…In our study population, nesting success was found to decrease with increasing conspecific density in the neighborhood of a territory (Müller et al 2005). We therefore predicted that probability of breeding dispersal is positively related to conspecific density around a territory (prediction 3a, Table 1).…”

“…In our study population, territory quality has been shown to influence local recruitment, with probability of recruitment increasing with territory quality (Müller et al 2005). If site choice is important for dispersal, we therefore expect probability of breeding dispersal to be negatively related to quality of the territories held in the year before dispersal (prediction 2a, Table 1).…”

“…forests, and, to a lesser extent, by gray alder (Alnus incana) forests, the river Inn, and a ravine. Further details on the study area can be found in Müller et al (2005).…”

“…The red-backed shrike usually breeds once per season, unless the first breeding attempt is not successful, in which case a replacement clutch may be produced (Glutz von Blotzheim and Bauer 1993;Müller et al 2005). Out of 475 breeding attempts of known status, 23.6% were replacement clutches.…”

Επίδραση Της Δομής Του Τοπίου Στην Ποικιλότητα Και Αφθονία Της Ορνιθοπανίδας Σε Αγροτικά Και Φυσικά Οικοσυστήματα

“…Επιπλέον, βρέθηκε ότι οι κτηνοτροφικές εγκαταστάσεις και τα γεωργικά κτίρια δεν επηρεάζουν τον πλούτο των πουλιών προτεραιότητας. Όσον αφορά στα είδη Lanius, αυτό μπορεί να οφείλεται εν μέρει στην οικολογία τους, γιατί προτιμούν ως ενδιαιτήματα αναπαραγωγής εκείνα που παρέχουν επαρκή κάλυψη για τις φωλιές τους (Muller et al 2005), ενώ χρειάζονται και περιοχές με διάσπαρτα δέντρα, θάμνους και φυτοφράκτες καθώς αυτές παρέχουν περισσότερες θέσεις εποπτείας και συμβάλλουν στην επιτυχή σύλληψη της λείας (Brambilla et al 2007 …”