with Wren Observations
Watch the videos here:
Bird lungs don't inflate much as they breathe, because the air passes through into huge air sacs. You can see how much of this wren's body is pulsing with air going in and out of the sacs as he sings. (How do we know this wren is a "he"?)
The next video shows a parent wren feeding the babies. Look carefully at the baby wren peeking out the hole. What part of its body is the easiest part to see? Why is the mouth so big?
Baby bird mouths are very conspicuous. The very sight of a baby bird's mouth triggers a response in the parents--they simply need to shove food into it!
The next video shows two parents returning repeatedly to the nest with food. Can you identify any of the insects? This videoclip is edited--there were longer spaces between the feedings than the video shows. But wrens return to the nest with food frequently throughout the day.
As you can see in the videoclip, wrens usually bring one food item to the babies each trip. From the second through the sixth day after the babies hatch, parents bring an average of 12-20 prey items to the nest per hour. After that until the babies fledge, the parents bring about 25-30 items to the nest per hour. Can you think of TWO reasons why the number goes up after day 6? Elizabeth Howard recorded the times the adults came to the nest with food for a half hour. She counted 31 visits with food during that time! How many visits per hour does that average to? Do you think the parents feed their babies that often throughout the day?
As soon as baby wrens swallow a morsel of food, they almost always back up and poop. We can't see the babies do this inside the bird house, but we CAN see the poop--because after a parent wren feeds its babies, it waits and then carries off the fecal sac. Watch the wrens grabbing and flying off with these sacs:
The sac that surrounds the poop is made of sugars and proteins. When the baby wrens are still very little, with little bacteria in their intestines, a fairly high percentage of the food goes through without being digested, and so the parents often eat the fecal sacs. But as the babies get bigger, the parents start carrying away the sacs. They usually carry them to a branch 15-40 meters from the nest and stick them on branches 2-3 meters from the ground.
To learn more about fecal sacs, look here:
If you have wrens nesting nearby, spend some time watching them. See if you can see the male singing, the parents feeding the babies, and the parents carrying away fecal sacs. Do your wrens behave like the ones in the video? Do you see any behaviors that aren't shown in the videos?
Also, take some time to look for insects. How many can you find in 15 minutes? How long can you look for insects before you get bored? Wren parents have to search for insects all day long, from sunrise until sunset. Would you make a good wren.