Greetings, Politics Thread. As usual, I wish everyone well during these challenging times. I hope birds can take some of the edge off. This week’s bird is another suggestion from my dad. He seems pretty invested in this little project and we could use some common ground, so I am happy to oblige. The mountain bluebird is a very small bird, weighing just 24–37g (0.85–1.31 oz) with a very large range throughout the north American continent. It lives year-round in the southwestern US, but migrates all the way from Alaska to Mexico if it lives in areas it would find uncomfortable during the summer and winter. This amounts to the longest migration among bluebirds. During these migrations it forms mixed flocks of up to 50 birds, and will travel alongside the related western bluebird as well as sparrows and juncos.
The mountain bluebird is a “secondary cavity nester,” a phrase I somehow had not previously come across in almost three years of bird-y headers. This just means that it likes to nest in preexisting spaces, whether holes in sandstone cliffs, holes in trees or birdhouses. The male will scout for nest sites to present to the female, who will ultimately decide where the family will nest. Once the site is selected, the female will build while the male stands guard, aggressively driving away any intruders on his new turf. Both members of the pair will defend the territory once the nest is constructed. Clutches will have up to five eggs. The birds will fledge in about three weeks, and will need around eight more before they are able to fend for themselves. It prefers high altitudes for nesting, usually over 2,100 meters (7,000 ft), and open grasslands, plains, etc.
Mountain bluebirds eat a varied diet mostly consisting of arthropods (grasshoppers, cicadas, beetles, larvae, etc) and fruits and berries. A source I used this week compared its hunting style to that of falcons, since it will dive down on prey or dart from its perch to grab a passing insect.
The most interesting thing I learned this week is the mountain bluebird’s unexpected relationship to humans. Numbers of these birds have been in sharp decline lately, dropping around 26% between 1966 and 2014. The reasons why were the source of my surprise. Reduced logging has meant a return of forests and fewer of the open plains the bird prefers. Also, better forest management has led to fewer fires, which also restrict the occurrence of the mountain bluebird’s favorite habitat. Although population numbers have stabilized recently, the American Bird Conservancy reports a real bummer: the PVC pipes used to mark out mining claims in the American west attract birds investigating potential nesting sites, in which they can become trapped and die. The organization is lobbying the Bureau of Land Managment and USDA Forest Service to remove or modify the pipes, and establish standards preventing their use. On the plus side, because they will take readily to bird houses and will congregate at feeders, it seems like there are some easy steps available to help these birds out.
Oh, right, finally, the title this week comes from research that shows the birds are strongly impacted by industrial noise in their habitat, which leads them to have high levels of stress and to produce more of a hormone called Corticosterone, a relative of the human stress hormone cortisol. Too much of this hormone leads to all sorts of negative outcomes for chicks and adult birds. There have been studies on the effects of this hormone on birds, and there is enough going on there that I will include a link to the relevant wikipedia article in my links section. Be kind to yourselves and each other, friends. I hope you are able to find a quiet, peaceful space this weekend.
Links: https://tinyurl.com/bddfbky7, https://tinyurl.com/3ckyjk3b, https://tinyurl.com/tdv9juu3, https://tinyurl.com/ync789cs, https://tinyurl.com/223wtuj6, Corticosterone info: https://tinyurl.com/2pyar79s