WHITE-THROATED SPARROW 13G7 



decrease over the period from the arrival of the females until the 

 young left the nest. Total areas occupied over the whole period 

 averaged 1.9 (0.9 to 3.2) acres for mated birds and 2.5 (1.5 to 2.8) 

 acres for unmated males. 



J. K. Lowther banded 47 males and 30 females on breeding terri- 

 tories in 1959; 19 males and 3 females were retrapped on the same 

 sites in 1960 and a careful search failed to reveal other banded birds. 

 It thus appears that males have a greater tendency than females to 

 return to the same territory from year to year. 



Courtship. — As will be described later, the white-throated sparrow 

 is a polymorphic species. For both males and females in winter and 

 nuptial plumages, two color types, based on the color of the median 

 crown stripe, were described — the white-striped and tan-striped 

 types.* Among breeding birds, there is assortative mating of opposite 

 types, a situation which is apparently unique among birds. Of 213 

 pairs caught and banded in Algonquin Park, 136 were of white- 

 striped males and tan-striped females, 70 of tan-striped males and 

 white-striped females, 6 of tan-striped males and females, and only 

 1 of a white-striped males and females. Therefore, white-striped 

 birds mate selectively with tan-striped birds. 



Investigations were made of behavioral differences between breeding 

 adults of both types in Algonquin Park in order to determine at least 

 some of the factors governing the assortative mating (Lowther, MS., 

 and see also Voice). Experiments with tape recordings showed 

 that white-striped males are more aggressive than tan-striped males 

 toward singing individuals. Furthermore white-striped females sing, 

 tan-striped females do not, and white-striped males act aggressively 

 toward singing females, while tan-striped males do not. Finally, 

 the trill note of a female elicits a copulatory excitation in males of 

 both types, but when the trills are accompanied by songs of either 

 males or females, this excitation of white-striped males is suppressed 

 and is replaced by aggressive behavior. This is not true for tan- 

 striped males, which were seen to copulate with their white-striped 

 females, even when a tape recording of a strange male was being 

 played. 



From these data, Lowther suggested a mechanism that might govern 

 the assortative mating in this species. As white-striped males act 

 aggressively toward any singing white-throat and white-striped fe- 

 males sing, then these males drive off any white-striped female and 

 thus mate only with tan-striped females. Alternatively, as songs of 

 male birds are supposed to attract females, which they do in the white- 



*The word "type" is substituted throughout this account for the author's 

 technically more accurate "morph" (see Lowther, 1961) which may not be 

 familiar to some readers. — Ed. 



