The bluebird is one of the most familiar tenants of the farm and dooryard. For rent the bird pays amply by destroying insects, and takes no toll from the farms crop.
~USDA Farmers Bulletin #513, 1913
I mentioned in an earlier post that I am trying to provide some video clips of what birds are feeding their young for an environmental education film called Hometown Habitat. The nesting season has passed for most local species, but, my friend, Alvin, informed me of a late Eastern Bluebird nest in a hollow log nest box at his house. Being one of the most recognized and beloved songbirds in the east, this is a species I really wanted to get for the project. So, in spite of the heat and humidity, I dragged my gear into Raleigh two days this week to see what I could capture.
It turned out that the nest box was in a great location for me to film while not disturbing the birds, and staying out of the heat of the sun. It was under the eaves of a shed that was visible from Alvin’s garage, so I set up the tripod just inside the garage and waited. It wasn’t long before the pair began bringing food to the young. I filmed a little over an hour on each of the two days. The first day I was there around mid-day and it was very hot, with temperatures in the 90’s. The birds seemed to take a little break from feeding in the heat (I don’t blame them), so I was only able to get a few clips. I decided to go back earlier the next day and that proved more productive.
I recorded trips to the nest box by both adults for an hour. In that time period, the birds made 12 trips with food. The female did most of the work, making ten of the twelve feeding trips. The male made two trips with food and three without as in the first photo above (more on that later). After looking at the clips, I could make out all but three of the food items brought to the nestlings. Of those I could identify, there were 4 caterpillars, 3 grasshoppers/crickets, 1 beetle grub, and 1 spider. Three of the caterpillars resembled Corn Earworms, but I can’t see enough detail to be sure. There is a corn field on some NCSU property just down the road, so it is possible.
These baby bluebirds probably have several more days in the nest based on Alvin’s observations. If you make some assumptions about the number of feeding trips during the nest cycle, you come up with some impressive numbers of insects and other food items brought in by the busy parents. Let’s give these bluebird adults an 8-hour workday (an underestimate, I am sure) with ten feeding trips per hour. Stretch that over the typical nestling period of 14 days and you get an impressive 1,120 feeding trips made by the parent birds (again, undoubtedly an underestimate). Then consider that many bluebirds nest two or three times each summer, and it is clear they are consuming a huge number of insects just during the nestling phase.
Here’s a short video clip showing the hectic life of parent bluebirds on a hot summer day.
The first bird in the clip, the male, flies out with a fecal sac after feeding the young. The female then brings in a grasshopper, checks for fecal sacs, and flies off.
While the female did most of the feeding in the two days I watched this year’s nest, the male did stay near the nest a little more. It seems there was something that disturbed him – ants. I noticed he flew to the base of the nest a few times while I was there and seemed to be pecking at something. Here is a short video clip I shot of this behavior:
When I looked carefully, I could see a line of tiny ants coming up the side of the shed and along the outside of the nest box. The male was obviously disturbed by this, perhaps recognizing that these can be a potential hazard to nestlings. On several occasions, he would sit at the base of the nest box and pick off ants as they crawled along the outside edge. Alvin was going to try to redirect the line of ants away from the nest after I left (perhaps with some well-placed petroleum jelly.)
Last spring, I photographed a different pair of Eastern Bluebirds bringing food to a nest box along a power line where I lived.
The difference in habitat made for some different prey items, most noticeably a lot of earthworms and large beetle grubs (probably June Beetles). I reported on this nesting cycle in a blog post last year. I remember being amazed then at the quantity, and size of some of the items on the grocery list for their young.
Every time I observe birds bringing food to their young, I am impressed by the amount of effort it takes and the skill these feathered hunters have in finding and securing prey. It also reminds me of how important adequate habitat is for their survival. We can all help ensure these birds continue to thrive by planting more native plants, protecting existing natural areas, and reducing our use of toxic chemicals in our surroundings. It is the least we can do as responsible landlords to such hard-working tenants.