A Closer Look At Bluebird Nests
I am a "wet-sider", a fourth generation Seattle resident. Despite this fact, I am frequently drawn east of the mountains to explore its wonders. I love the geology. I thrill at the first whiff of Ponderosa pine forest on a dry day.
I don't often bird just for the sake of birding. Most of my extended outings are those that involve volunteerism. Data collection for YVAS bluebird trail has been an important part of my spring and summer planning for the last few years. This year I added a twist and volunteered to help Dr. Terry Whitworth in his collection of nests to study Protocalliphora sp. flies. These flies look, at a glance, like regular houseflies. However they parasitize nestlings and take blood from them. After several larval stages they pupate in the nest and emerge as adults. Dr. Terry has identified many new species of this fly and continues his life work in documenting these flies in an effort to determine their effect on nestlings. By involving myself in two studies I could justify the frequent trips to the trail. In years past I usually did two or three trips to the upper half of the trail, boxes 64 through 125. This year I visited many more times, once after the official monitor dates to collect nests and clean boxes.
After a long, rain drenched winter/spring I needed a dose of the dry side. Warm weather, dry air, wild flowers and bird song. It refreshes the soul. My first trip, on May 1 started out sunny enough but before too long, I had to pull out my wool sweater. Most of the boxes had nests starting; a few had eggs. This was the earliest I had ever visited the trail. By the time I got to Umtanum Falls trailhead I was concerned. Darn it, it was cold! Just about then it started snowing. Not the big fluffy flakes of the wet side but little powdery fluffs. It was snow none-the-less.
My next visit a week later convinced me that these birds are tougher than I thought. A bounty of Mountain Bluebirds greeted me. Most boxes had nests in them and many of these nests had eggs. Chipmunks seemed in short supply. A few House Wrens sassed off, but none were yet using houses in this area. On this day I met one particular Mountain Bluebird. He had firmly staked out box 74 as his. Nearby a House Wren made a fuss when I visited but the Mountain guy kept him at bay. His box held 5 eggs and he did not waver from his nearby post while I checked. No fuss, no flap. He fixed me with a little black eye and kept me well in line. There was no female to be seen.
A visit a month later revealed a baby boom. Some boxes had already fledged so I started my nest collecting. Along with the Protocalliphora many nests held beetles, crickets and remnants of bird meals. I am sure Dr. Terry and his assistant were kept busy sifting through this bounty. Mr. Box 74 watched calmly as I cleaned out the nest that had fledged five new bluebirds. Still no female to be seen. A House Wren fussed from a nearby rock pile and flapped around defending its space.
All along the road there were birds, birds, birds. Many more Mourning Doves than I ever remember seeing. There was a noticeable lack of Meadowlarks. I decided that the Sage Thrasher rivals the Black-headed Grosbeak for lovely song, though the thrasher could use a drink of water to match the liquid quality of the grosbeak. A pair of Brewer's Blackbirds gave away their secret and I found their nest on the side of the road. It held one egg and one still wet hatchling. I had seen an adult fly out with the eggshell!
As the season progressed I came to see the ups and downs of these bird families. Dead nestlings and non-viable eggs are a fact of life. Do they relate to the weather? The flies? It is a bad parasite that kills its host. During a season of marginal weather or poor food production it may be something that pushes them over the edge. Perhaps this is normal failure rate. I am sure Betsy Martin will put all the numbers together and come up with comparisons. Looking for nests of other species in the environment was challenging and the few that I found here were out of reach. I had a wonderful time watching wrens nesting in a fence post. Flycatchers nest right out in the open on tree limbs but blend in so well!
Mr. Box 74 had built a new nest. Instead of lining his nest with the usual feathers and such, he had found some bits of black plastic and had added these unique touches to his nest cup. Neighbor House Wren was keeping a low profile, no doubt with nest chores. All along the trail, empty nest boxes showed that many new bluebirds had joined the population ranks. Chipmunks had started making their presence known by stuffing the boxes with their fluffy grass nests. There is some evidence that the chipmunks might be raiding eggs and nestlings in some of the boxes so we are encouraged to evict the four-leggers.
Starting in July I visited the lower half of the trail, boxes 1 - 63. This environment is markedly different from the upper half. Trees support and encourage wrens. Many boxes held wren nests. If you have not seen these nests for yourself, you are missing a treat. Densely packed with twiglets from the pine trees, the tops support soft cups. Last year I remember snakeskin as the lining of choice. This year feathers and fluffy fur seem to be in style. One nest was lined with long hairs that look as if they may have come from an elk. Wren eggs are lovely pink with maroon speckles. The clutches are large and when they hatch, it can be a guess as to the number of occupants. I am a real softie for these guys.
Western Bluebird appears to favor the lower half of the trail with its wooded areas and open pastures. I was concerned that the population was not well represented on the upper half and was interested to discover this population split. The boxes along this area of the trail are much more hidden on tree trunks and finding them was an adventure. Even on my third trip I had to back track to catch up one or two I missed. They are right on the road at this point and their being hard to spot is a good idea. In cleaning one box, I was dismayed to find that someone had opted to put his or her beer can inside. The box had been cleaned previously, but sheesh! On my first trip in May I tried to pick up as many cans and bottles around the stops I made as I could. I filled a 50-lb. rice sack. This might be a great spring get together. A box repair, garbage-busting get together. (Ed. Note: Come along next year for our annual clean-up, repair, and garbage pick-up!)
I returned one last time on August 14 to clean out all the boxes I could. There were still hatchlings in some of the boxes. Mr. 74 was nowhere to be seen. His neighbor, the House Wren, took his departure as an opportunity to stuff the box with sticks. While cleaning out wren nests, it certainly appears that they move in quickly to nest on top of old bluebird nests. It will be interesting to see what Dr. Terry comes up with as far as parasites from these two bird species. I am also interested to see what he says about bluebirds that build new nests on top of old.
I am looking forward to next year and all the new discoveries to be made in this now familiar place. I hope next year I can call upon other box volunteers to gather the nests. A more complete picture of the parasite population may be valuable. I thank Betsy Martin for her extra efforts on this project and for her help with nest data I needed for parasite studies.
- Marti Anderson