|Pine Siskins often feed in groups or flocks
While many northern species of birds fly south through central Texas during fall migration, some species go no further, and spend their winters in the area. Our generally mild winters and higher availability of food sources are the reasons they stay, fueling themselves in the cooler months as they prepare for northward migration in the spring.
This cycle is not always predictable, however, as there are a few overwintering bird species that are nearly absent in some years, and overly abundant in other years. One such species is the Pine Siskin (Spinus pinus), a small finch-sized, seed-eating bird with a sharp pointed bill, short notched tail, and streaky brown overall with subtle yellow edging on the wings and tail. They flash yellow wing markings as they flutter while feeding or burst into flight, and usually occur in fairly large, gregarious flocks. Their wheezy twitters are a dead giveaway, and they will stay all winter near a dependable food source.
|Pine Siskin showing the yellow edging on wings and tail
Pine Siskins range widely and erratically across North America every winter in response to seed crops, and flocks may monopolize your feeders one winter and be completely missing the next. In the winters when Pine Siskins are abundant, the phenomenon is referred to as an irruption. In the bird world, irruptions, broadly defined as sudden changes in population density, refer to the movement of northern-wintering bird species to the south in years of low food availability. However, some recent bird banding studies suggest that some pine siskins fly west to east while others fly north to south in search of winter food.
While fairly common, the overall population of Pine Siskins is difficult to estimate due to their unpredictable seasonal movements. However, this species is considered to be in steep decline, with an estimated 69% decline in numbers from 1966 to 2019. Natural threats include predation by outdoor domestic cats, squirrels, hawks, and jays. Man-made threats include pesticides, mineral deposits from salts used to melt ice and snow, outbreaks of salmonella from unsanitary feeders, and forest clearing.
|Pine Siskins will quickly empty your feeders!
Winter flocks of Pine Siskins can be aggressive around food sources, often trying to disrupt and challenge feeding competitors by lowering their heads and spreading their wings and tail. They may even lunge toward and pick fights with other seed-eating birds such as Lesser Goldfinches and House Finches. Keep an eye on your feeders this winter and you just may witness this irruption disruption, when flocks of these birds can eat you out of house and home!