Transgenerational immunity in a bird–ectoparasite system: do maternally transferred antibodies affect parasite fecundity or the offspring's susceptibility to fleas?

During egg formation, female birds deposit antibodies against parasites and pathogens they were exposed to before egg laying into the yolk. In captive bird species, it has been shown that these maternal immunoglobulins (maternal yolk IgGs) can protect newly hatched offspring against infection. However, direct evidence for such benefits in wild birds is hitherto lacking. We investigated (1) if nestling Great Tits Parus major originating from eggs with naturally high levels of maternal yolk IgG are less susceptible to a common, nest-based ectoparasite, (2) if maternal yolk IgGs influence nestling development and in particular, their own immune defence, and (3) if there is a negative correlation between levels of maternal yolk IgG in host eggs and the reproductive success of ectoparasitic fleas feeding on the nestlings. Counter to expectations, we found no indication that maternally transferred yolk IgGs have direct beneficial effects on nestling development, nestling immune response or nestling resistance or tolerance to fleas. Furthermore, we found no negative correlation between host yolk IgG levels and parasite fecundity. Thus, whereas previous work has unequivocally shown that prenatal maternal effects play a crucial role in shaping the parasite resistance of nestling birds, our study indicates that other egg components, such as hormones, carotenoids or other immuno-active substances, which bird females can adjust more quickly than yolk IgG, might mediate these effects.     

SONG INHERITANCE AND MATING IN A SONGBIRD WITH LOCAL DIALECTS

ABSTRACT

In this paper we document the pattern of geographic variation in song of the Corn Bunting in a marked population in Sussex. Song variation is best described as a system of local dialects with three song types in each dialect. We examine the inheritance of dialects from father to son; sons sing the same dialect as their nearest neighbour, rather than inheriting the dialect of the father. Therefore songs seem to be learned after dispersal. We also compare the dialects of mates and fathers of females: our results suggest that females do not rely on dialects when pairing. These results are discussed in the context of the current controversy surrounding other species with dialects and hypotheses relating dialects to the genetic structure of populations.     

Evaluating Cementum to Determine Past Reproduction in Northern Sea Otters

Abstract: Age at first reproduction (AFR) has been difficult to quantify in mammals, as the most commonly used methods require reproductive tracts or direct observations. However, work in several large mammal species suggests that the width of cementum light bands in teeth decline once females begin to reproduce, suggesting that teeth structures might provide a new tool to examine AFR. To determine if changes in cementum light band width could be used to calculate AFR for the northern sea otter (Enhydra lutris kenyoni), we measured cementum light band widths on sectioned premolar teeth and compared them to reproductive tracts. We classified otters as parous if any single light band was narrower than a threshold value, selected as the value that minimized error rates. At a threshold value of 0.32, we correctly identified otters as parous or nulliparous in 83% of cases (n = 92) as compared to reproductive tracts, and the AFR estimated from teeth samples (3.52 ± 0.032 yr) was not different from that determined by reproductive tract analysis (3.45 ± 0.031 yr; t-test, P > 0.05). These data support the use of cementum as an indicator of past reproduction in individual female otters, which can then be used to estimate average AFR. Given that declines in cementum width have been described for other mammal species, the same quantitative approach used here could be applied to other species. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):618–624; 2008)