by Rosemary Jann
It must be an indication of how preoccupied I’ve been lately: I didn’t realize the mockingbirds were nesting again until their scratchy chat call exploded over my head as one buzzed me crossing the yard.
Northern Mockingbirds are fond of the native honeysuckle (Lonicera sempervirens) in our yard, especially for their first nesting of the season. According to the Audubon Guide to North American Birds, mockingbirds raise upwards of two broods a year but don’t reuse their nests, opting instead for a new site in their territory. The trumpet honeysuckle provides a protective tangle of vines at their preferred nesting height, 3 to 10 feet off the ground. Native to North America, they have adapted especially well to suburban environments, which provide mowed lawns for foraging, tall telephone lines for surveilling their territory, and nearby shrubs for shelter. I don’t know whether these are the same birds that were here in past years, but Wikipedia notes that suburban mockingbirds often return to sites where they previously bred successfully.
Of course, the best-known trait of Mimus polyglottos is signaled by their name, which means “many-tongued mimic.” Although both sexes mimic, the male is especially prolific in adding new songs throughout his lifetime (up to 200 in all, according to Cornell Lab’s guide, All About Birds). In suburban settings, these can include not just the songs of other birds and animals (like cats), but also common sounds like car alarms and ringtones.
Their noisy aggression is equally distinctive, however. Cornell states that scientists debate the purpose of the male’s characteristic flashing of the white patches on his wings. Is it intended to startle insects, to intimidate rivals, or, like his song repertoire, to help attract a mate?
Their often-displayed aggression against other creatures can also serve multiple purposes. They use their chat call as they run off territorial rivals and while attacking nest predators. I had seen mockingbirds dive-bombing cats; I was puzzled when witnessing a particularly vicious and prolonged attack on a hapless squirrel, until I learned that they too predate on eggs and nestlings. Crows and other larger birds are also nest robbers, which explains why the mockingbirds were so violent in driving off some crows casing their nesting site in our yard last week. Mockingbirds apparently endorse the belief that the best defense is a good offense.
Aggression plays a role not just in natural selection but also in sexual selection. A high level of aggression in the male signals to the female that he is likely to be more invested in the parenting process and therefore deliver more nesting success. This is important, says the Animal Diversity Web page on Northern Mockingbirds, since both build the nest, both feed the chicks, and the male educates the nestlings while the female starts building a new nest. So, if you find yourself annoyed by the aggressive behavior of this noisy backyard neighbor, it may help to understand that the mockingbird’s feistiness plays an important role in its survival—and to wear a hat if you can’t avoid being dive-bombed on the way to the car.