It's the off-season for me, and that means less time spent watching birds, and more time watching my computer. As much as I love being outside, it's actually a really exciting time to look at all the data we collected over the last three years, and get a chance to sit down and really see what the birds are telling us about the plants and insects in our backyards.
If you've read my other blogs from 2013-2015, you may remember that I'm a PhD student who works within Neighborhood Nestwatch studying how non-native plants affect food resources for Carolina Chickadees. We put up nest boxes in backyards all over the DC metropolitan areas, monitor chickadee nesting success, survival and behavior.
This 2015 season we continued monitoring chickadees at more than 150 different sites, and more than 50 of those were new to the project this year! Here's a recap of our season.
- We monitored 57 chickadee nests of which 20 were successful at raising young to fledge. Our low success this year was due to abundant House wrens that kicked many of our chickadees out of their boxes.
- We color-banded 95 new adult chickadees and 66 nestlings.
- We also re-sighted 63 chickadees that returned from previous years.
One of the questions I've decided to tackle first is to see whether chickadees prefer to forage and breed in yards that have more native plants. In August I attended an ornithological conference in Nova Scotia where I presented some preliminary results. The title of my talk was "Behavioral Responses by Carolina Chickadees to Non-native Vegetation". I got a lot of great feedback from other chickadee researchers and was very grateful receive an award for "best PhD student paper" by the Association of Field Ornithologists.
The questions I addressed in this talk were threefold: Are native trees more likely to support:
- Caterpillars for chickadee food?
- Chickadee breeding?
- Chickadee foraging?
Turns out, the chickadees are actually pretty picky birds! Our color-banded birds preferred to feed in native trees at almost every single yard we studied. In addition, oak trees were the top preferred tree in 70% of the yards. Our insect data suggests that oaks also tends to support a high abundance of caterpillars too, so it makes perfect sense that chickadees would spend most of their time foraging in them when they are available.
In fact almost all the trees that were most preferred by chickadees were natives that supported many different species of caterpillar. For example:
- Native oaks (supports 534 caterpillar species)
- Native maples (supports 297 caterpillar species)
- Native cherries (supports 456 caterpillar species)
- Native elms (supports 215 caterpillar species).
Our most abundant caterpillar in the spring is the Fall cankerworm (Alsophila pometaria), a common 'inchworm' caterpillar that can be found on many different tree species. Their name refers to the adults which are active in the fall, but the caterpillars hatch and begin feeding as soon as the leaves begin to emerge in late April through May. This caterpillar can cause some tree damage, but fortunately for us, chickadees and other backyard birds love eating cankerworms. By providing wildlife habitat, birds can help keep caterpillar populations down for trees, and birds get an abundant protein-rich food source to feed their young. It's a win-win situation to support food webs in your backyard.
For the rest of this winter, I'll be looking at some of reproductive data to see if there are any consequences to chickadees when they breed in areas with more non-native plants. I'll also be making plans for our data collection in 2016. Wish me luck!