Bird Club Zoom Meeting
November 18, 2020
Presiding: Doug Wentzel
Recording: Peggy Wagoner Saporito
Treasurer’s report (Jean Miller): $50 spent on last
month’s presenter; $130 received in dues. (To send your annual
dues by mail, see website)
Next spring, Millbrook Marsh Nature Center will be hosting
socially distanced weekly bird walks at their facility beginning
March 23. Doug Wentzel and Jon Kauffman will be leading some of
these walks, but additional volunteers are needed. Anyone
interested in leading walks, please contact Doug.
The Pennsylvania Game Commission will soon be working to improve
Woodcock habitat in Stone Valley. Commission officials
indicated that Stone Valley is one of the best areas of the state
in terms of woodcock numbers and habitat potential.
Thanks to Jen Lee for volunteering to be State College Christmas
Bird Count compiler. She will be working with Bob Fowles who
continues as co-compiler. And thanks to Greg Grove for recruiting
Christmas Bird Counts in the area have been set. For more
information, see Audubon’s 121st CBC: Map
of Active Circles
December 19 Penns Creek (including Penns Valley) (Cathy Pierce)
December 20 State College (Jen Lee and Bob Fowles)
December 20 Huntingdon (Deb Grove)
December 27 Bald Eagle State Park (Bob Snyder)
December 28 Lake Raystown (Jon Kauffman)
Interesting Bird Sightings: Greg Grove’s Summary
(late Oct-mid Nov)
Fall migration is winding down but eruptions of Northern winter
finches are ramping up with many reports of Evening Grosbeaks,
some Red Crossbills and Redpolls. There are still a few shorebirds
around and 11 different warbler species were reported during the
period including unusual sightings such as Orange-crowned,
Tennessee and Common Yellowthroat. Some encouragingly high counts
of Rusty Blackbirds have been reported. Marsh Wrens, Tree and Fox
Sparrows have also been around in somewhat higher than usual
numbers. At the hawk watches, Golden Eagles have been passing
through, concentrated on days with strong northwest winds, and
even a few Rough-legged hawks, which are more typically seen later
in winter, have already been reported in the area.
Speaker: Allison Cornell: “Life in the Nest Box: Nestling
development in American kestrels”
(This presentation (missing the first minute) can be viewed here).
Allison, now an assistant professor of Biology at PSU Altoona,
described work she had recently conducted in Eastern Pennsylvania,
in collaboration with Hawk Mountain Sanctuary and Cedar Crest
College, to study American Kestrel nestlings in nest boxes located
on farms with suitable short grass and pasture habitat.
American kestrels are of concern because number of adult pairs and
percent nest box occupancy has dropped 50-60% since the early
1990’s in the 100+ nest boxes monitored by Hawk Mountain staff.
Apparently, the number of fledglings that survive to adulthood, to
raise chicks of their own, has declined over time. Habitat loss,
predation by Cooper’s hawks, West Nile Virus and lower overwinter
survival have all been speculated in this decline.
By studying nestling development and subsequent fledgling health
and survival, population declines can begin to be addressed.
Nestlings of all species face challenges as they achieve
developmental milestones, particularly when transitioning from
nestling, a sedentary lifestyle, to fledgling, a very active
lifestyle. Mortality rate is high among many different species
during the first month after fledging, often due to predation.
Survival and reproduction is influenced by an animal’s behavior,
morphology, physiology and biochemistry. To study some of these
factors, Allison focused on morphology and physiology of nestlings
as well as parent behavior in terms of prey delivery to
chicks. She monitored nests in 2018 and 2019 during the
first 3 weeks of nestling life prior to fledging, which occurs
during the 4th week.
Prey delivery by parent birds was monitored with cameras located
just outside of nest boxes. Early in the season, rodent and
passerine prey dominated and later in the summer, arthropods such
as crickets and grasshoppers, constituted a larger portion of
Nestlings’ weight increased quickly, approaching adult weight,
during the first 2 weeks, then plateaued prior to fledging. As
with adults, female nestlings tended to be somewhat heavier than
male chicks. Feather growth in both sexes, as shown by wing chord
length, progressed linearly until fledging.
To monitor chick physiology, weekly blood samples were drawn to
measure hematocrit and hemoglobin levels. As nestlings prepare for
fledging, transitioning to an active life of flight requiring
greater aerobic capacity, higher hematocrit and hemoglobin levels
would be expected. However, of the 58 chicks monitored, there was
no clear pattern; hematocrit and hemoglobin increased in some and
decreased in other nestlings over the 3 week blood monitoring
period. It is unclear what is causing these variations. Nestling
diet may be a factor.
Allison is planning on studying this in greater detail with a
supplemental feeding study. By manipulating nestling diets,
Allison hopes to understand how diet impacts nestling development
and subsequent fledgling health and survival.