A starling is not the same as a cowbird. While they may share some similarities in appearance, they are actually different species of birds.
One key difference between a starling and a cowbird is their bill shape. Female Brown-headed Cowbirds have a thick conical bill, which is well-suited for cracking open seeds and foraging on the ground. On the other hand, European Starlings, including juveniles, have a long and pointed bill, which they use for probing and capturing insects.
Another difference is in their behavior and breeding habits. Brown-headed Cowbirds are known as brood parasites, meaning they lay their eggs in the nests of other bird species. They do not build their own nests or raise their own young. Instead, they rely on other bird species to incubate their eggs and raise their offspring. This behavior is quite unique among birds. European Starlings, on the other hand, are not brood parasites and they build their own nests to raise their young.
In terms of appearance, female Brown-headed Cowbirds and juvenile European Starlings can appear somewhat similar, especially when they are not in breeding plumage. Both have a dark brownish coloration, but there are some key distinguishing features. Cowbirds have a shorter tail compared to starlings, and their overall body shape is more compact and stocky. Starlings, on the other hand, have a longer tail and a sleeker, more slender body shape.
It is also worth mentioning that male Brown-headed Cowbirds have distinctive glossy black plumage and a brown head, while male European Starlings have iridescent black feathers with speckles of white and a yellow bill.
In my personal experience as a birdwatcher, I have encountered both Brown-headed Cowbirds and European Starlings in the field. While they may occasionally be mistaken for each other, careful observation of their bill shape, behavior, and overall appearance can help in correctly identifying these birds.