Backyard Birds – Spring Bluebirds

Around our patch in Franktown, Urling and I have seen very few bluebirds this spring; they seem quite scarce. We saw a couple of flocks of Mountain Bluebirds fly through in late March, but none since. As of April 12, we’ve seen one to three pairs of Western Bluebirds along the Cherry Creek Trail and an occasional one along our road.

This seems like a paltry count, so I compared this year with the three prior years’ data. In the past three years, we saw both species almost daily starting in mid-March. This drop seems striking, at least along our road and on the trail we walk regularly.

I posted this on the Audubon group, Douglbirds (for birds in Douglas & Elbert counties) and received some responses with similar observations.

Karen Metz of Frankton said: “I have seen possibly 60% fewer Western Bluebirds on three-mile walks in my neighborhood. At my own home so far this spring, only one female and two males have shown up. I offer mealworms and peanut butter cakes, both relished by bluebirds, and, in recent years, I typically see eight or more  by late March. I was feeding between 75-80 Western Bluebirds on my property last year in October.”

Kathy Dressel, also from Frankton, emailed on April 9: “This spring I have seen only five Western Bluebirds coming to the feeders in my yard so far. I have two females and three males. At Castlewood Canyon State Park, I saw one bluebird on a box as I drove into the visitor center this last Tuesday. I was feeding between 75-80 Western Bluebirds on my property last year in October.”

Barbara Spagnuolo said on April 8, “I can report, although informally, that I did not hear or see many bluebirds while I visited various nest boxes around Castle Rock for box maintenance & repair this season. In fact, despite visiting fourteen different sites between the first week of March and yesterday (always on calm sunny days), I heard/saw bluebirds only twice. That is definitely very low compared to previous years.

“But I can also report more specifically that we found only three complete nests and five incomplete nests in our 190 nest boxes last week during the first week of monitoring, compared to five complete nests and almost a dozen incomplete nests during the first week of monitoring in 2020. We, too, have a very detailed monitoring program with extensive data keeping since 2007, so we will have a good opportunity for data comparison at the end of the season.”

David Suddjian posted that as of April 14, “At Ken Caryl Valley where it occurs as a regular migrant and which has several breeding pairs, I have so far had just two encounters with Mountain Bluebirds this season. Compared to the past three years, this is only 15-25% of the frequency detection for the same time period. I’ve checked some of the spots that often have nesting pairs, but none were present on those checks.

“I visited South Park in Park County on Apr 13, driving and birding for about 7 hours through prime Mountain Bluebird habitat. I tallied 19 Mountain Bluebirds through the day, mostly as singles, well distributed but considerably fewer in number than expected based on past visits similarly timed in April. Compared to my own observations on other visits in the 2^nd week of April, the numbers of Mountains were about 25-30% of what I tallied in prior years.”

On the other hand, Peter Ruprecht posted this note from Boulder County: “Bluebird migration, as visible from my home on the west side of Superior, was a little different than usual this year. Normally I’ll see small flocks of Mountain Bluebirds passing by intermittently over a period of several weeks. This year, I only saw them for three days (around March 23-26) but there were at least a hundred each day, sometimes in flocks of 40-50.

“There have been some good-sized flocks (30+) in other areas of South Boulder County since then, but not near my house. Overall, I’d say the total number I’ve seen this year is higher than usual.”

With the new snow, more people have started to report bluebirds. On April 15, Leslie Handerson emailed, “I heard bluebirds last week near Hwy 86 in Elizabeth, but none in my yard (about one mile away). Tonight just before sunset, I saw three that went to my feeder where I have put dried worms and some other stuff in for the last few years.  They also seem to be flying to one of the houses nearby that was nested in last year.  So it seems they are returning visitors from prior years. I’m glad they’ll have food tomorrow with the snow.”

Curt Frankenfeld analyzed eBird reports for the last three years. Essentially, they show that a normal number of bluebirds spent the 2021 winter in Colorado, but the number of migrant bluebirds dropped. For Douglas County, where they arrive in mid-March, numbers of both species dropped in March and April.

Curt also discussed the 2020 fall die-off event. “An iNaturalist study concluded that the fires in the Northwest, California, and the Mountain West were key events that contributed to the die-off. A compounding event was a sudden drop in temperature with accompanying high winds in the NW (that helped bring an end to the fires). The study looked mostly at the direct effect on the birds but did not really account for the food-chain interruptions due to these same events. That includes things like the insects lost in the fires and the concentration of the bird populations around the fires now eating every surviving insect. Note that there were some bluebirds discovered in this mass die-off, but it seems to be a relatively small proportion.

“Studies from New Mexico concentrate a lot on the weather in New Mexico around the time of the die-off. They, too, had a major storm that brought wind, precipitation, and cold to the state. The storm occurred two to three days before masses of dead birds were discovered in the state. They speculated that the already stressed birds simply could not handle the winds and cold of the storm. The New Mexico papers all seem to state that the birds were starving—with the cold, there may not have been insects to support them even if they came to ground.”

Bluebird monitoring this year will provide some more definitive trends than our mostly anecdotal notes of despair.