I went to Nachusa Grasslands last month in the hopes of seeing the bison that roam around there. And I did!
In the past, cowbirds would follow herd of bison to consume the seeds and insects that were stirred up by the large animals, however with modern farming and ranching they have become much more common in developed areas (The Guardian: Zoology). Their previous nomadic lifestyle following herds of bison is believed to be the reason for their parasitic behavior, since nesting wasn’t practical when constantly on the move (The Guardian: Zoology). The Brown-headed Cowbird does not make its own nests, but rather lays white and brown eggs in the nests of other birds which require incubation for approximately 10-13 days (Tekiela, 1999). Because of the time and energy saved from their parasitic behavior, females are able to lay up to three dozen eggs each season (The Guardian: Zoology). However, because of the advantages the Brown-headed Cowbird has received from agriculture and pastoralism, their numbers have increased at a rate that hasn’t allowed other species to catch up (The Guardian: Zoology). Because of this, many species have not yet evolved a defensive strategy against inadvertently raising cowbirds instead of expending the energy on their own young (The Guardian: Zoology). The Brown-headed Cowbird is the only parasitic bird species in Illinois and have been known to lay eggs in the nests of over 200 different species of birds (Tekiela, 1999). They are social birds and often move in large flocks (The Guardian: Zoology). Although they are a migratory species that heads to southern states, they can still be seen throughout Illinois year-round (Tekiela, 1999).
In addition to geese though, there was also a lot of litter at these stops including some discarded fishing gear. Fishing gear can cause a lot of problems for wildlife so if you do fish, make sure to clean up properly. If you can’t for whatever reason, then you shouldn’t be fishing.
I’ll be sure to get these photos (and more) onto my site (when I get around to it ;D).
Tekiela, S. (1999). Birds of Illinois: Field guide. Cambridge, Minn.: Adventure Pub.