Field experiments have shown that parents in the colonially-nesting cliff swallow (Hirundo pyrrhonota) discriminate between their offspring and unrelated young whereas parents in the closely-related but noncolonial barn swallow (H. rustica) do not, and that discrimination is based on the chick begging call. In a laboratory experiment, we trained three cliff swallows, two barn swallows and a European starling (Sturnus vulgaris) to discriminate among chick begging calls of the two swallow species. All birds discriminated more easily among the calls of different cliff swallows than among the calls of different barn swallows, suggesting that cliff swallow calls are more individually distinctive, and may be adapted for a signature function. Moreover, cliff swallows discriminated among both cliff swallow and barn swallow calls faster than did the other birds, which is consistent with a perceptual adaptation for conspecific calls that incidentally facilitates the discrimination of similarly-structured heterospecific calls.

Cliff Swallow (Hirundo pyrrhonota) chicks were played calls of parents and unrelated (control) adults at 9 and 18 days of age. Younger chicks showed no difference in the frequency of their antiphonal begging calls to parental vs. control calls. The older, near-fledging chicks, however, responded significantly more to parental calls than to control calls: 78% of their total antiphonal calls were in response to parental playback calls. In these older chicks, the degree of preference correlated with the measured acoustic differences between the parent and control calls. The results indicate that Cliff Swallow chicks are able to recognize their parents by voice before they leave the nest. Offspring recognition of parents is discussed as it relates to the evolution of parent-offspring recognition systems in general.

We tested the hypothesis that memory or perceptual limitations imposed by song repertoires contrain the ability of song birds to recognize their neighbours by song. Using operant conditioning procedures, we trained male song sparrows (Melospiza melodia) (median repertoire size = 8) to discriminate between two artificial song sparrow repertoires of 32 songs each (64 songs total). Both song sparrows learned to discriminate concurrently between all 32 song pairs. The birds learned later songs as quickly as they learned earlier songs. These results suggest that song sparrows are capable of memorizing the full song repertoire of their neighbours under natural conditions. In a second experiment we found that song sparrows readily generalize from one exemplar of a song type to other variations of that song type. We conclude that the evolution of song repertoires of song sparrows have neither constrained nor been constrained by individual recognition of neighbours by song.

Microscopic and analytical studies of the lipids in the heart and muscle of the BIO 82.62 myopathic hamsters and age-matched normal animals at the average ages of 33, 67, and 108 days were performed. Microscopic examinations did not show increased lipid depositions in the hearts of the diseased animals as was found in the BIO 14.6 strain. No consistent differences in the lipid content of the cardiomyopathic hamsters (BIO 82.62) and age-matched controls were observed in the three age groups except in the cholesterol content of muscle. Cholesterol increased significantly (P less than 0.01) in the 67 and 108 day old animals. This increase elevated the cholesterol/phospholipid ratio. Analysis of the fatty acid composition of triglycerides showed that the cardiomyopathic hamsters store more saturated fatty acids in both heart and muscle than do their normal counterparts. The abundance of more saturated fatty acids may imply that either the desaturation mechanism is altered in the diseased animals or that unsaturated fatty acids are preferentially utilized in other processes.

To ascertain the usefulness of Mongolian gerbils as an inbred model for otitis media, 52 Mongolian gerbils (Meriones unguiculatus, strain MON/Tum) were compared with 26 chinchillas (Chinchilla laniger) for susceptibility to Streptococcus pneumoniae type 3, Haemophilus influenzae type b, and a polymicrobic culture including anaerobes (Streptococcus intermedius, Propionibacterium acnes, Staphylococcus epidermidis, and Corynebacterium sp.). Organisms were inoculated percutaneously into the superior chamber of the middle ear bulla. The gerbils and chinchillas shared similar susceptibilities and responses to the inoculated organisms as determined by X-ray, otoscopic, histopathological, and microbiological determinations at 5 to 7 days. Koch's postulate studies proved the role of S. pneumoniae and H. influenzae in the pathology found in both animal models. The animals were also susceptible to the polymicrobic culture, although the relative virulence of the individual members of this mixture was low, suggesting that these species potentiated as a polymicrobic mixture. The Corynebacterium sp. appeared to elicit the greatest histopathological response in chronic (8-week) studies in gerbils. The gerbils were found to be useful as an alternative animal model for the study of otitis media of bacterial etiology. bils to otitis media when inoculated with Streptococcus pneumoniae type 3, H. influenzae type 802 on July 16, 2020 by guest