We know that human kids grow, mature, and gradually move towards a life that is independent of their parents’ home. The same is true for baby birds: they also have to decide when the time is right to leave the nest and start on their journey to independence. This seems to involve a balancing act between making sure they are big and healthy enough to survive independently, while leaving the nest quickly to avoid predators.
Our last post shared some pretty intense videos of predation events at nests. In both videos all of the chicks got eaten, and the parents either fled or did not approach the nest while the predator was there. The badger and the 13 lined ground squirrel weren’t challenged as they made off with nestlings. It’s not always like this, though. It turns out that bird parents respond differently depending on who is trying to eat their chicks.
While adult birds and eggs are vulnerable during incubation, they are at even greater risk after chicks hatch. Most of our grassland birds are altricial as chicks, and need to stay in the nest long enough to be reasonably mobile when they fledge. However, chicks are also very vulnerable in the nest: they stay in one place, and the noise and activity surrounding the nest can attract predators. These birds need to balance the benefits of staying in the nest until they are able to fly to forage and escape predators with the potential risks of being found by predators while still in the nest.
A lot of people really dislike - even hate - cowbirds. I get it. It can be hard to watch a small warbler trying to keep a huge cowbird chick fed, and it’s sad when host species eggs get destroyed. But objectively and unemotionally, cowbirds are amazing, smart, resilient, and cool. Their reproductive strategy allows them to produce many more offspring than the average bird. Hopefully by the end of this post, you’ll be thinking about cowbird behavior in a new light too.
Grassland bird nests are just about my favorite things ever. They’re perfect little secrets hiding in the foliage, holding precious babes. I love the way they are often fairly similar, but have subtle differences that let you identify who built them. (Sparrows are my favorite group of birds, which might explain why I love small brown things that look alike!) Nest searching is tricky business too -- and it feels like an incredible accomplishment when you find one.