Signals for Parent-Offspring Recognition: Strong Sib-Sib Call Similarity in Cliff Swallows but not Barn Swallows

We tested the prediction that the calls of sibling cliff swallow (Hirundo pyrrhonota) chicks are more similar than those of sibling barn swallow (Hirundo rustica) chicks. This prediction was derived from the hypothesis that the call of the colonial cliff swallow, but not the call of the noncolonial barn swallow, has been selected for signature function (i.e., for individual distinctiveness). In Study 1 we examined the calls of 22 cliff swallow sibling pairs and 23 barn swallow sibling pairs. The intraclass correlations for 4 of the 5 cliff swallow variables were significantly different from zero, and each of the 4 was approximately 0.5. Only one of the 4 barn swallow call variables was significantly different from zero. In a discriminant-function analysis of these data, cliff swallow chick calls were correctly identified as to sibship in 82 % of the cases, barn swallow chick calls in only 46 % of the cases. In Study 2 we cross-fostered eggs between cliff swallow nests to create foster sibships (all chicks in a nest were unrelated). We found no similarities among foster sib calls, and thus no evidence for call imitation of the calls of sibs or parents, suggesting that genetic differences are the main source of variance in cliff swallow chick calls.     

Song Perception in the Song Sparrow: Importance of Different Parts of the Song in Song Type Classification

Song sparrow (Melospiza melodia) males have repertoires of 6 to 12 song types, each song consisting of four or five contrasting phrases. Song types vary both within individuals (a singer varies successive renditions of a type within a singing bout) and between individuals (neighbors sing slightly different versions of a type), and in both cases this variation is concentrated in the later parts of the song. We speculated that type variation in the later parts of the song might be correlated with a perceptual tendency to classify song types primarily on the basis of the earlier parts of the song. We tested this hypothesis using a laboratory conditioning technique, supplemented by a field playback experiment. In the lab, song sparrows and white crowned sparrows were trained to discriminate between two distinct song types. In test sessions, they were presented with hybrid songs synthesized from varying proportions of the two training song types. For most birds and most song pairs, song classification was influenced by all parts of the song, with the beginning elements being most important. The field playback experiment used song type matching as the response measure. Each subject was presented a hybrid stimulus song consisting of the first half of one of his song types and the second half of another of his song types. Subjects replied with both ‘front matches’ and ‘back matches’ (60% were front matches).     

Adaptation of protein metabolism to endurance training. Increased amino acid oxidation in response to training.

This study was conducted to investigate alterations in excretion of urea and total nitrogen after6-8 weeks of daily exercise and to establish if the capacity for amino acid oxidation in muscle is influenced by endurance training. Urea nitrogen excretion was increased in trained compared with untrained rats and nitrogen balance was less positive in trained than in untrained rats. Increased [14C]leucine oxidation with training was observed both in vivo and in vitro. The results of this study demonstrate that amino acid catabolism is increased during exercise training and that the muscle enzymes involved in leucine oxidation adapt to endurance training in a manner similar to the enzymes of carbohydrate and fat catabolism.     

Polyquarternary amines prevent peptide loss from sequenators

Automatic spinning-cup sequenators are often incapable of approaching the carboxy terminus of a peptide because of the mechanical loss of material (washout). We report here an adjunct, polyquarternary amines, specifically Polybrene, that greatly reduces or eliminates this problem.     

Parent-offspring recognition in bank swallows (Riparia riparia): II. Development and acoustic basis

In study 1, bank swallow (Riparia riparia) chicks were exchanged with like-aged chicks from other broods. Parents accepted chicks that were transferred into their nests at age 15 days or younger; rejection began to occur at 16 to 17 days. In study 2, chicks' vocalizations were recorded in the burrow. We found that an immature begging call given by young chicks is replaced by a ‘signature’ call at 15 to 17 days of age. An acoustic analysis suggested that these calls are individually distinctive. Study 3 was a playback experiment designed to test whether the chicks' signature calls are a sufficient cue for parental recognition. We found that parents would approach a speaker broadcasting the calls of their chicks in preference to one simultaneously broadcasting the calls of alien chicks. The pattern of results suggests that parental recognition is based on the chicks' signature calls and that development of recognition is dependent on the development of the call.     

Lesions of the anterior forebrain song control pathway in female canaries affect song perception in an operant task

Sexual behavior in female rats, typified by the lordosis reflex, is dependent upon estrogen action in the ventromedial nucleus of the hypothalamus (VMH) and its surrounding neuropil. However, the synaptic organization of this brain region remains unclear. Pseudorabies virus (PRV) was used to transneuronally label the neural network that innervates the lumbar epaxial muscles that execute the lordosis response. PRV-labeled neurons were identified within and subjacent to the VMH four days after injection of PRV into the back muscles. The pattern of labeling was defined in relation to three landmarks: the VMH core, as defined by Crystal Violet staining; the shell, as defined by the oxytocin fiber tract; and the cluster of estrogen receptor-containing cell nuclei. The pattern of PRV labeling in the VMH displayed a striking rostral-caudal gradient. In general, many of the PRV-labeled neurons were found in the oxytocin fiber tract, with far fewer in the core of the VMH. Furthermore, PRV-labeled neurons were rarely found in the cluster of estrogen receptor-containing neurons, and less than 3% of the PRV-labeled neurons were double labeled for estrogen receptor. The results suggest that oxytocin may directly influence these lordosis-relevant VMH projection neurons, whereas estrogen may have transsynaptic effects.     

Functional aspects of song learning in songbirds

The oscine passerines, or 'songbirds', are one of the few animal taxa in which individuals learn their vocal signals. Recent comparative studies reveal a remarkable diversity of song-learning strategies in the songbirds. Here, we discuss recent studies that shed light on the possible functional basis of different song-learning programs. We argue that further insights into the evolution and ecology of song learning will require that comparative data and functional hypotheses be analyzed in a phylogenetic context, and we review recent studies that we feel might be the first steps in this process.