We have been asked here at the Gulf Coast Bird Observatory quite often this winter, by folks up and down the Upper Texas Coast and inland… where are the winter birds? Folks are missing seeing their American Robins, American Goldfinches, Cedar Waxwings, and other bird species that often (normally) spend the winter with us.
Many of the “missing” birds are called an irruptive species. They are not true winter migrants in the sense that each year they always migrate south at the same time or to the same location. Irruptive species do “migrate” but only when and where they need to. Their migration (or lack thereof) depends on the weather and the food source. If it is a mild year up north and food is in ample supply, they stay put. Or they migrate east and west instead, in search of food if it’s mild there, or just move south a short distance where they can find a good supply of food. The name irruptive species comes from those years when they irrupt in big numbers into a different area for winter.
I can attest to this, as I recently lead a birding trip to Duluth, MN. They still have American Goldfinches there now, which they never do in winter! This explains why we are not seeing certain species right now. They are still north of us, not needing to travel farther this year.
Birds that we see every winter such as Orange-crowned Warblers and Yellow-rumped Warblers are more of regular winter migrants. They move south each year when the number of hours of daylight triggers the urge to move south. But even some of those species may not make it all the way down to us each year in the same big numbers. We always have some of these birds, but in some mild winters maybe not as many, as they stopped short of us a bit. Why expend all that energy and take the risk of traveling further when one doesn’t need to?
Bird species such as Snow Geese seem to be shifting their migration pattern altogether. The warmer winters, on average, are keeping them further and further north, even though there are severe winter storms that effect their migration as well. This is not a good development as they are outcompeting themselves for food in those habitats and, at times, starving to death.
In general we do have less birds than we did before. About 30% less since 1970, actually. That is a huge decrease in bird numbers in such a short time! And it is noticeable, especially in some bird species. The reasons are many, including habitat loss and development that have threatened birds for some time, but it is also due to such things as birds hitting cars, windows, cell towers, sky scrapers in huge numbers… by the millions each year. Outdoor house and feral cats also claim millions of birds each year in the US alone! It’s not easy to be a bird! They need all the help we can give.
