State College Bird Club
November 16, 2016
State College Bird Club Minutes: November 16, 2016
President Diane Bierly called the meeting to order at 7:00 with 23 people present. Jim Curtis recorded minutes.
Diane read the minutes from the previous meeting and gave the
Treasurer’s report: $280 deposited since the last meeting with no
No field trips are currently planned. Diane reminded everyone that dues are due and that local area CBCs are coming up soon.
From the audience Betty Kirchner, our liaison to Foxdale, asked if we
would like to meet over dinner sometime, i.e., have a dinner meeting at
Foxdale’s dining facilities.
The list was called with 108 total species. No outstanding rarities, but a nice representation of birds for this season.
Diane introduced our speaker for the night. Matt Toenies is in
the second year of his M.A. work in PSU’s Department of Ecosystem
Science & Management, and presented his research titled “Winners
and Losers in the Changing Bird Community of Hemlock Forests”.
Basic points presented as premises to his research study were:
1) Invasion of hemlock woolly adelgid, illustrated
with maps, has caused extensive and very systematic damage to hemlock
forests, and always results in death of the tree.
2) The unique structure of hemlock forests provides
important contributions to the environment and specifically the bird
community. Hemlocks hold on to their lower branches, decreasing
understory growth and increasing diversity of bird species.
3) Six species were selected to represent bird
species with close association to hemlock forests: black-throated green
warbler, Acadian flycatcher, blackburnian warbler, blue-headed vireo,
winter wren, and hermit thrush.
Matt’s hypotheses were presented in the form of a diagram illustrating
the process of change on hemlock forests due to adelgid intrusion,
including change in the habitat structure and the impact of this shift
in vegetation on bird species.
The research consisted of a baseline study in the Delaware Water Gap
area looking at pre- and post-adelgid invasion conditions. The method
was based on point counts done on 2 visits per season, with counts
including estimated distance to the birds, a survey of hemlocks in the
point count areas, and an evaluation of understory density.
In the results, impact on vegetation of adelgid invasion was recorded
by graphs demonstrating the relationship of hemlock health and
understory density. Predictions of the impact on bird populations were
presented in graphs relating habitat status to specie characteristics,
and the data included taking “occupancy modeling” – i.e., the
probability of detecting a given specie – into account.
Matt presented many graphs showing various species’ responses to
hemlock decline and, fortunately for Matt, trends were as predicted.
Not willing to leave it at that, Matt looked into variation in bird
community composition across sites for further support of his
hypotheses. Specifically, he looked at vegetation attributes to
differentiate sites, divided bird species into groups associated with
specific site characteristics, then explored the responses of these
species groups to the different characteristics of post-adelgid
These results, presented in another series of graphs, were probably not
as strong as he anticipated. Basically, the species group most closely
associated with hemlock forests did show declines in relation to
habitat degradation from the adelgid invasion, but not in the
unambiguous, direct relationship we might expect. Nick Bolgiano asked a
series of questions that pushed Matt to tighten up this analysis.
Matt closed his presentation with the broad observations that
hemlock-associated species are declining but holding on, and that bird
communities are changing with change in habitat.
Questions from the audience included:
1) How severe is the situation in Centre County? Matt
said that it was not bad, but only a matter of time before the impact
of the adelgid becomes more advanced. In this region the severity of
winters is the key.
2) Are there ways to change the study to show a
stronger effect on hemlock-related species? Here Matt fell back on the
universal desire of researchers for more data, in this case in the form
of more sites.
3) Is there evidence that hemlock-associated species
have some ability to successfully switch habitats? This question, which
also implies the fundamental issue of whether those species labelled as
“hemlock-associated” may not be so strongly hemlock associated after
all, kind of got lost in the inevitable decline of energy in the room
as the meeting nears its end . . .
And with that, Diane thanked the speaker, he received polite applause, and the meeting was adjourned.
Minutes by Jim Curtis