I note that the area of my observation last night was in private open space of Ken Caryl Ranch. It does not have public access. However, I do offer DFO trips that visit there, so there is that opportunity.
David Suddjian Ken Caryl Valley Littleton CO Sent from my iPhone > On Sep 4, 2021, at 5:43 PM, David Suddjian <[email protected]> wrote: > > > I love going out on summer evenings to the Hogbacks near my home to listen > for Common Poorwills. It is always a beautiful experience, and sometimes > extra interesting, too, with good visual or auditory encounters with the > poorwills. But on the whole, I don't learn a whole lot about what the > poorwills are up to in that evening time. They are hard to view, often heard > only a distance up the slope. and the oft unseen calling birds reveal little > obvious about age, sex, nesting status, local breeder v migrant, etc. And > most of what I encounter are calling birds, heard some distance away, and > most often unseen. > > But I don't feel too bad. The limited literature on Common Poorwill biology > and natural history shows there are many unknowns. The Birds of the World > species account offers a good summary of what is known and not known, and for > the Common Poorwill the sections on behavior, foraging and nesting are pretty > slim. > https://birdsoftheworld.org/bow/species/compoo/cur/introduction > There is not a lot of detailed information. Under "Priorities for Future > Research" it begins "Poorwills are one of the least understood of North > American birds, probably owing to their small size, cryptic coloration, > nocturnal habits, and long periods of dormancy during winter. Future > research on the species should address issues along two distinct avenues: the > basic biology of the species, which is unclear..." [longer excerpt under my > signature line] > > For one example, the account indicates a lack of information from the wild on > how or if poorwill parents feed their young after fledgling, or how long > parents tend to their young after fledging, if young remain in the natal > area for some time after fledging, and how young beg or solicit feeding. > > <IMG_1099.jpg> > Dakota hogback slopes on the left, Lyons hogback slopes on the right. > > Now, at the end of summer, there are usually good numbers of Common Poorwills > in the hogbacks of Ken Caryl Ranch. They live on the slopes of the higher, > eastern Dakota formation hogback, and on the slopes of the western Lyons > formation hogback. Both slopes are mostly grassland, with areas of foothill > scrub, oak woodland, and lots of exposed rocks in some areas. Last night I > tallied about 12 poorwills as I walked along a 0.6 mile segment in the vale > between the two hogbacks. The first calling poorwill began 25 minutes after > sunset and the last poorwill was noted 43 minutes min after sunset. The dusk > bout of calling was typical for late summer, with individuals overlapping > their vocalizations, and some calling very near to each other. The calls are > the primary call 'poor-will' but the quieter third element of the call is > usually very hard to hear now from most calling birds. I also have noticed > that individuals calling for a time will make periodic shifts in frequency. - > calling steadily, then increasing the frequency for a several seconds, before > returning to the somewhat slower rate of delivery. > > <IMG_1496.jpg> > This view shows the slopes where I observed two poorwills, described below. > > Last night things unfolded as per usual. I made my way to my starting point > and waited until sunset came and went. There is very little bird sound out in > the hogbacks at evening now, and I only heard Lesser Goldfinches and several > scrub-jays. The poorwills began calling after sunset, and eventually I began > to walk back over my 0.6 mile segment. Part way along, a poorwill was calling > from a slope on the Lyons side where I have had many sightings of poorwills. > I paused and scanned with my bright flashlight. Far off, I caught the > eyeshine the poorwill, calling from a perch about 100 yards up the slope from > the valley bottom. I moved closer and could see the bird was perched on the > tip of a mullein stalk, which they like to do. It was now over half an hour > past sunset, and pretty dim. At this distance, even with a bright light, the > body of the poorwill is hard to see through the binoculars, but its bright > eyeshine showed exactly where the bird was. Often there is just one dot of > eyeshine, as I can often see only one eye. So you see one bright dot shining > back. Now, a flying bird shows eyeshine, too, but its dot of light drifts > around over the dark slope as the bird flies low over the grassland. > > https://ebird.org/checklist/S94159518 > > So I'm watching the perched bird dimly, and listening to its call (recordings > on the eBird checklist above). Then I notice the glowing eyeshine dot of a > second poorwill that is flying low over the same slope. This flying bird is > foraging and is not calling. Whenever the flying bird approached the perched > bird, the perched bird briefly increased its calling rate, The flying bird > flew right up to the perched bird, and there seemed to be very brief contact > or nearly so, and the flying bird then drifted off and resumed foraging low > over the slope. I saw at least 5 such close visits by the flying bird to the > perched bird over a few minutes. Then the foraging poorwill moved out of > view, and the calling bird took flight and flew across the valley between the > hogbacks, landing somewhere up the Dakota slope. > > So I saw one perched bird calling regularly, and a second bird foraging in > flight nearby. The flying bird repeatedly visited the perched bird, at which > time the perched bird responded by changing the nature of its calling. The > rate of calling can be heard on the 2nd recording on the checklist, at 3 > seconds and again at 34 seconds. It is subtle. > > As I thought about what I had seen, I realized that it was not different from > what juvenile swallows do (for example): They sit on a perch, sometimes > begging, and wait to be fed. The adult comes around and feeds them and flies > off to get more bugs. I am wondering if my perched poorwill was a juvenile > being fed by an adult. The Birds of the World species account indicates there > is no information about how young are fed or for how long. If that was what > was happening, it suggests to me (based on character of calls) that many > calling poorwills I hear now in the dusk chorus could be young of the year, > and that they are from local nestings on or near their natal territories (vs. > migrants moving through). > > In the end, I try to fit a piece into the puzzle of a mysterious, little > known, but prominent species of our Front Range region. But I'll have to go > back out again to see and hear more. > > David Suddjian > Ken Caryl Valley > Littleton, CO > > From Birds of the World species account: > Excerpt from "Priorities for Future Research" > Although widely distributed, poorwills are one of the least understood of > North American birds, probably owing to their small size, cryptic coloration, > nocturnal habits, and long periods of dormancy during winter. Future > research on the species should address issues along two distinct avenues: the > basic biology of the species, which is unclear, and the physiological aspects > of heterothermy by poorwills, many of which are particularly intriguing. > > Reproductive success -- both numbers and factors influencing -- is > essentially unknown except at the northern periphery of the range and > findings there, where some populations could be ephemeral, are unlikely to be > representative of the species as a whole (Csada and Brigham 1994a, Macdonald > et al. 2003). Data on long-term survival of individuals are also lacking, > although results in Arizona suggest this species is not an especially > long-lived bird (Woods 2002). Juvenile survival and natal fidelity are > unknown, as no banded poorwill nestling has been recovered in a subsequent > year. More importantly, no migratory bird banded on its breeding grounds has > been recovered in winter, and thus the winter ranges of migratory populations > are entirely speculative. > > > -- -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/cobirds?hl=en?hl=en * All posts should be signed with the poster's full name and city. Include bird species and location in the subject line when appropriate * Join Colorado Field Ornithologists https://cobirds.org/CFO/Membership/ --- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/27C4D71F-F1A3-457A-B51A-968A967E739F%40gmail.com.
