Postcopulatory sexual selection reduces Z-linked genetic variation and might contribute to the large Z effect in passerine birds.

The X and Z sex chromosomes play a disproportionately large role in intrinsic postzygotic isolation. The underlying mechanisms of this large X/Z effect are, however, still poorly understood. Here we tested whether faster rates of molecular evolution caused by more intense positive selection or genetic drift on the Z chromosome could contribute to the large Z effect in two closely related passerine birds, the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (L.

Group display in the socially monogamous Northern Double-collared Sunbird (Cinnyris reichenowi).

Several sunbird species (Nectariniidae) exhibit group display, but the function of this behaviour still remains unclear. We test two hypotheses (reproductive tactic and joint territory defence) to explain the function of this behaviour using data gathered on Northern Double-collared Sunbirds (Cinnyris reichenowi) from the Cameroon Mountains. Sunbirds exhibited group display throughout the breeding cycle.

Sex differences in impaling behaviour of Great Grey Shrike Lanius excubitor: do males have better impaling skills than females?

Prey impaling in shrikes Laniidae is considered to be a feeding adaptation to dismember and consume large prey and is unique among food-storing animals. However, other exaptations of this behaviour were recorded, including signals in mate choice, where cache size is a sign of male quality. Thus, due to a strong sexual selection, male and female birds might differ in their behavioural patterns of impaling behaviour.

Ecological character displacement in the face of gene flow: evidence from two species of nightingales.

Background: Ecological character displacement is a process of phenotypic differentiation of sympatric populations caused by interspecific competition. Such differentiation could facilitate speciation by enhancing reproductive isolation between incipient species, although empirical evidence for it at early stages of divergence when gene flow still occurs between the species is relatively scarce. Here we studied patterns of morphological variation in sympatric and allopatric populations of two hybridizing species of birds, the Common Nightingale (Luscinia megarhynchos) and the Thrush Nightingale (L.

Blood parasites in two co-existing species of lizards (Zootoca vivipara and Lacerta agilis).

We investigated the occurrence of blood parasites of two lizard species: the common or viviparous lizard (Zootoca vivipara) and the sand lizard (Lacerta agilis) in western Poland. Selected traits of lizard body morphology were studied with respect to the presence and intensity of haematozoan infection in blood samples collected from 218 adult lizards; 88 of the common lizard and 130 of the sand lizard. Haemogregarinid blood parasites were found to be the common parasite of both lizard species in studied locality with prevalence 39.

Settling decisions and heterospecific social information use in shrikes.

Animals often settle near competitors, a behavior known as social attraction, which belies standard habitat selection theory. Two hypotheses account for these observations: individuals obtain Allee benefits mediated by the physical presence of a competitor, or they use successfully settled individual as a source of information indicating the location of high quality habitat. We evaluated these hypotheses experimentally in two species of shrikes.

Densities and morphology of two co-existing lizard species (Lacerta agilis and Zootoca vivipara) in extensively used farmland in Poland.

The study was carried out in extensive farmland area near the town of Odolanów, Poland. During two breeding seasons (April-May, 2006-2007) lizards were counted on transect routes and captured by hand or by noosing. In total, 123 specimens of L.