Different patterns of allopreening in the same-sex and opposite-sex interactions of juvenile large-billed crows (Corvus macrorhynchos)

Allogrooming, where an individual grooms another, has been extensively studied in various social animals to understand its role in the evolution of cooperation/prosociality. In existing studies in mammals, allogrooming has been suggested to exhibit not only a hygiene but also a social function. Allopreening, a topic of increasing interest in mammals but recently also in birds, has been studied mostly with mature animals. However, in some species immature individuals also show allopreening and its function remains poorly understood. Crows, Corvus spp., are an ideal model to study this phenomenon, because juveniles form year-round aggregates during their long juvenile stage (e.g., throughout 3–4 years). Here, we investigated the function of allopreening in juvenile groups of wild-caught large-billed crows (C. macrorhynchos). Allopreening frequency and duration for three groups of wild-caught juveniles were analysed to determine whether there was a symmetrical (i.e., reciprocal) or asymmetrical allopreening pattern, and if sex composition of the dyad and/or relative dominance of donor and recipient had an effect. We found that both the frequency and duration of male allopreening correlated with frequency of aggression. Allopreening between both males and females occurred unidirectionally from dominants to subordinates but not in the opposite direction. On the contrary, allopreening between a male and a female was found to be reciprocated, though the absolute frequency and duration were both greater in males than in females. These results suggest that the social function of allopreening in juvenile crows differs depending on the sex composition of the dyad, functioning as a dominance signal for same-sex dyads, and serving a social bonding function for opposite-sex dyads. These findings may reflect the potentially crucial roles of allopreening in within-sex competition and opposite-sex attraction during the 3 year-long juvenile stage affecting future mate choice in lifelong monogamy.     

Nestedness of hoopoes' bacterial communities: symbionts from the uropygial gland to the eggshell

How microbial symbionts are established and maintain on their hosts is a leading question with important consequences for the understanding of the evolution and functioning of mutualistic relationships. The acquisition by hosts of mutualistic microbial symbionts can be considered as colonization processes of environments (i.e., host) by symbionts. Colonization processes can be explored by characterizing the nestedness of communities, but this approach has rarely been applied to communities of microbial symbionts. We used this approach here, and estimated the nestedness of bacterial communities of hoopoes (Upupa epops), a species with symbiotic bacteria in their uropygial gland that are expected to colonize eggshells where they protect embryos from pathogens. Bacterial communities were characterized by ARISA (Automated rRNA Intergenetic Spacer Region) and studied the nestedness characteristics of bacterial communities living in the uropygial secretion, bill, belly and eggshells of each sampled female hoopoes. We detected a consistent nested pattern of bacterial communities of hoopoes; from the uropygial gland to the eggshell. We also found evidence of study year and reproductive events influencing the level of nestedness of bacterial communities of hoopoes. These results indicate that bacterial communities of eggshells and body parts of female hoopoes are at least partially conditioned by the symbiotic community in the uropygial gland. We discuss the importance of these results for understanding this host–microbial mutualism functioning and evolution.     

Colourful male European Serins Serinus serinus are more careful with their plumage

Ornamental traits typically advertise individual condition and can be costly to maintain. Plumage maintenance behaviour can increase plumage quality and positively influence female mate preference. We investigated this prediction by performing female mate‐choice trials and measuring male plumage maintenance behaviour in the European Serin Serinus serinus. More colourful males spent more time in plumage maintenance than less colourful males, but this was not correlated with body condition or ectoparasite load. Females preferred more colourful males, although this was not influenced by male plumage maintenance. Our findings highlight the fact that investment in plumage maintenance depends on individual coloration and this may reinforce the honesty of ornamental plumage and convey positive information for mate choice.     

Causation and influence of environmental enrichment on feather picking of the crimson-bellied conure (Pyrrhura perlata perlata)

This study examined the effect of environmental enrichment on feather picking in the crimson-bellied conure Pyrrhura perlata perlata. A total of 10 conures was observed, 8 of which showed minor to severe plumage problems. In a pre-enrichment period the conures were observed without changes in the environment to assess their social behavior and activity patterns, in particular, feather picking behavior. Feather picking was self-inflicted; furthermore, conures with plumage problems spent more time on all comfort activities, including preening, and less time on flying and vocalization. In three successive periods, several enrichment materials were tested to examine whether, and how environmental enrichment altered their behavior. The conures preferred natural and edible enrichment materials over less natural ones. Observed changes in activity patterns were an increase in locomotion and a decrease in preening behavior. However, no improvement of the plumage was visible during the weeks of observation. The results suggest that environmental enrichment was successful in altering the behavior of conures, but had only a stabilizing effect on existing plumage problems. Zoo Biol 16:161–172, 1997. © 1997 Wiley-Liss, Inc.     

Host defence mediates interspecific competition in ectoparasites

1. Interspecific competition influences which, how many and where species coexist in biological communities. Interactions between species in different trophic levels can mediate interspecific competition; e.g. predators are known to reduce competition between prey species by suppressing their population sizes. A parallel phenomenon may take place in host-parasite systems, with host defence mediating competition between parasite species. 2. We experimentally investigated the impact of host defence (preening) on competitive interactions between two species of feather-feeding lice: 'wing' lice Columbicola columbae and 'body' lice Campanulotes compar. Both species are host-specific parasites that co-occur on rock pigeons Columba livia. 3. We show that wing lice and body lice compete and that host defence mediates the magnitude of this competitive interaction. 4. Competition is asymmetrical; wing louse populations are negatively impacted by body lice, but not vice versa. This competitive asymmetry is consistent with the fact that body lice predominate in microhabitats on the host's body that offer the most food and the most space. 5. Our results indicate that host-defence-mediated competition can influence the structure of parasite communities and may play a part in the evolution of parasite diversity.     

Seasonal changes in blue tit crown color: do they signal individual quality?

Plumage coloration is generally perceived as a static traitand therefore not a good indicator of current condition. However,changing of feather colors after molt does occur and may haveimportant implications for signal function and sexual selection.We studied longitudinal changes in blue tit (Parus caeruleus)crown ultraviolet (UV)/blue color, a sexually selected trait,by repeatedly measuring the same individuals between early winterand late spring. Whereas crown UV reflectance (UV chroma andhue) decreased dramatically over time, brightness and saturationdid not show consistent patterns of change. The magnitude ofthe decline in coloration exceeded sexual and age dichromatismin hue and UV chroma, respectively. Hence, seasonal color changescould have strong effects on blue tit sexual signaling. Between-individualvariation in the decline in UV coloration was large and relatedto attributes of male, but not female, quality, such as sizeand condition. Thus, conspecifics could potentially gain informationabout male phenotypic quality by assessing color change overthe year. However, the degree of decline in male UV color didnot affect breeding success because neither the number of within-pairnor the number of extrapair offspring produced correlated withchanges in crown color. Seasonal changes in the expression ofplumage coloration are probably widespread, and maintainingplumage coloration could thus constitute an additional honesty-enforcingmechanism after molt is completed.     

The distribution of mallophaga on the domestic pigeon (Columba livia)

The distribution of Hohorstiella lata, Colpocephalum turbinatum, Campanulotes bidentatus compar, and Comlumbicola columbae on domestic pigeons were determined. Each species laid its eggs on a different part of the body but all fed on the fluffy part of the body feathers. H. lata also fed on blood, and C. turbinatum on its own eggs and nymphs. Reduction of the efficiency of preening led to an increase in the number of lice and more widespread distribution of nymphs and adults but not to a rapid change in the distribution of eggs. It is suggested that preening has played a major selective role, and that the morphological and behavioural adaptions of the lice are to ensure that they and their eggs survive this type of predation.