[cobirds] Broad-tailed Hummingbird phenology at Grandview Cemetery, Fort Collins (Larimer)

As has been reported, at least three active Broad-tailed Hummingbird nests are known at Grandview Cemetery (Fort Collins, Larimer) this breeding season.  The Birds of North America (BNA) account for this species was authored by the Calders.  William, now deceased, studied this species for about 20 years at the famous Rocky Mountain Biological Station at Gothic, CO.  Much of the account is based on his diligent work, along with that of his wife Lorene. 

 

So far, two of the three nests at Grandview have already produced fledged young (2 from each nest per the norm).  At present, the third nest, well behind the others, apparently still has eggs being incubated.  Calder shows the earliest Broad-tailed Hummingbird eggs being laid around May 20.  Doing the math (eggs 16-19d, nestlings 21-26d) and calculating back, this puts the egg deposition period for the southwestern corner nest (which yielded free-flying young somewhere between June 10 and June 14) at April 26th (earliest potential date) or May 8th (latest potential date).  The intriguing "tripledecker" nest in the southeastern corner yielded young around 18June, putting egg deposition onset somewhere between May 4 and May 12.  The slower (more "normal"?) nest in the center showed egg deposition (a guess based on how the female acted) at somewhere between June 10 and June 15, egg hatching somewhere between June 26 and July 3 (Calder shows the latest date for the egg stage being about 10July), with fledging anticipated sometime between July 17 and July 24. 

 

Gothic is 9,485 feet ASL.  Fort Collins is right at 5000 feet ASL.  For what it's worth, even adjusting for the elevational difference (however one would do that), it would seem this spring's egg-deposition for the southwestern and southeastern cemetery nests was earlier than Calder found during his long-term study. 

 

Egg hatch for the central nest should be in about a week, which would put it about normal, even a bit late, for a mountain nest.  Mama looks real bored and has added a narrow rim of lichen, bark, and conifer pitch bits to the nest while she waits.  She can't know (can she?), but the cemetery is a lot safer place for LIFE at present than the foothills 5-20 miles to the west.

 

Dave Leatherman

Fort Collins