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Juveniles learn songs from more than one neighbor and preferable learn songs that their neighbors share (Beecher et al. 1994; Nordby et al. 2000). A possible explanation for this observation is that juveniles eventually set up their own territory next to these neighbors, sometimes even replacing one (Beecher et al. 1994; Nordby et al. 1999). Nordby et al. (2000) also points out that juvenile song sparrows preferably learn songs their first-year fellow juveniles learn. In fact, juvenile cohorts’ songs can even be more similar to each other than to those of the early tutor (Kroodsma&Pickert 1984). This is more evidence showing the importance of sharing songs with neighbors, because there is a good chance that cohorts will become neighbors once they settle their own territory.
Settling and maintaining a territory is very important to male sparrows. Territory ownership affects major areas in a bird’s life, including nesting, inter- and intraspecies competition, and food collection, all of which have implications for mate attraction and offspring survival (Nice 1941). In song sparrows, males (and their partner) essentially gather all of his food from within his territory and males with a good territory often come back to it year after year. This illustrates the importance of finding a good territory (Nice 1941).
Best (1977) studied the field sparrow ( Spizella pusilla ) to see the effects of territory quality on mating success. He found that males with better territories mated more frequently. Territory quality was measured based on territory size and presence of certain favored plant species. Other factors that affected territory quality include snake and mammalian predation and cowbird parasitism (cowbirds have been observed to place their eggs into the nests of many species of sparrows). The presence of these factors often led to the female’s desertion (Best 1977). Much of these findings can be applied to our sparrow species.
Songbirds also exert great effort to learn songs of their neighbors; juveniles hone their songs continuously after settling a territory to better match those of neighbors. DeWolfe et al. (1989) notes that juvenile song sparrows that are first settling a territory have up to four songs, but after settling, they keep only two of the closest songs to those of their neighbors. This suggests that juveniles anticipate becoming territorial neighbors to their tutors, and therefore learn from them to ease communication, since territorial neighbors are required to interact with each other in many ways. Wilson et al. (2000) argue that the amount of song-sharing indicates a male’s competitive ability to obtain a preferred territory near his tutors. Song sharing may also determine a male’s effectiveness in using songs to communicate aggressively. To provide further evidence, another Beecher group showed that the number of songs a sparrow shares with his neighbors is correlated with length of possession of his territory, because neighbors depend on shared songs to regulate territories and interactions with each other (Beecher et al. 2000, Burt et al. 2001). A bird that does not share songs with its neighbors will have a hard time communicating with them and be successful in his territory (Beecher et al. 2000). This shows the importance of learning as an adaptive function. Without learning, there is no guarantee that a songbird will share songs with its territorial neighbor.
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