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Song variation in a population of chestnut-sided warblers (Dendroica pensylvanica) was investigated during 1970–1972 in Hillsboro County, New Hampshire. Five song types, which appear to be shared by all males in the local population, are described and are used differentially by the birds. Two 'accented ending' song types are used primarily by undisturbed males located centrally on their territories. Two 'unaccented ending' song types are used in territorial encounters, or when a male is located peripherally on his territory. The fifth type, 'jumbled song,' is used almost exclusively during territorial encounters. There is no evidence of special association of any of the types with male–female interactions. It is suggested that the song types form a graded series of signals, increasing the efficiency of male–male communication by transmitting more precise messages than would be possible with only a single song type.

Discrete geographic variation, or dialects, in songs of songbirds arise as a consequence of complex interactions between ecology and song learning. Four of the five species of Zonotrichia sparrows, including the model species White-crowned Sparrow (Z. leucophrys), have been studied with respect to the causes and consequences of geographic variation in song. Within White-crowned Sparrows, subspecies that migrate farther have larger range size of dialects. Here, we assessed geographic patterns of song variation in the fifth species of this genus, the Golden-crowned Sparrow (Z. atricapilla). We analyzed field-recorded songs from 2 sampling periods (1996-1998 and 2006-2013) covering most of its breeding range in western North America. All songs began with a descending whistle and most songs consisted of 3-4 phrases that contained combinations of whistles, buzzes, and trills. We identified 13 discrete song types based on unique sequences of phrase types and frequency changes between phrases. Over 90% of individuals sang 1 of 5 song types, and we found clear dialect structure composed of these 5 common song types. The geographic range of dialects spanned large distances (500 to 1,700 km), resembling the geographic structure of dialects in the long-distance migrant Gambel's White-crowned Sparrow (Z. l. gambelli), though locations of dialect boundaries differ between species. Because both Golden-crowned Sparrows and Gambel's White-crowned Sparrows migrate similarly long distances, our study provides support to the hypothesis that dialect range size correlates with migration distance. We found little evidence of change in dialect composition in 4 populations that were sampled 15 years apart, which suggests that the dialect structure is stable across multiple generations. Our study opens the door for further comparisons to investigate links between ecology and the emergence of song dialects in this well-studied genus.

Territoriality of snowy owls (Nyctea scandiaca) was investigated near Calgary, Alberta, in the winters of 1976–1977 and 1977–1978. Males appeared to be nomadic, although some individuals remained in small areas for periods of up to 17 days. Many females defended territories of 150–450 ha for periods of up to 80 days. Territories of females contained some habitats in excess of their proportion on the study area. This represents selection of habitats with high prey availability. Owls spent more time in such habitats than in resource-poor habitats within their territories. Territory size was inversely related to the proportion of stubble field and the amount of "edge" habitat bordering stubble fields, on the territories. These findings are consistent with an earlier hypothesis that the size of feeding territories is regulated to provide the territory holder with a constant level of food. Juvenile females defended larger territories than did adult females, with higher proportions of nonpreferred habitats. We suggest that these differences result from the inexperience of juveniles in selecting and defending optimal winter territories.