Great Blue Heron (GBHE) Rookery Monitoring
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Skyhawk drone 4.1.18
Great Blue Heron (GBHE)
Rookery Monitoring
2018
Donna Taylor and J.W. Pieper
06/21/2018
This document summarizes the data obtained during the 2018 monitoring season of the Great Blue
Herons located at the Cibolo Preserve in Boerne, Texas.
CIBOLO PRESERVE
GREAT BLUE HERON (GBHE) and GREAT EGRET (GREG)
ROOKERY MONITORING
2018
Rookery monitors: Candace Andrews, Rheda Boardman, Susan Bogle, Coco Brennan, David
Doss, Janet Ferrill, Brenda Fest, Gary Fest, Linda Gindler, Sarah Hilburn, Tom and Patsy Inglet, Terry
Lashley, Janet Ledbetter-Ferrill, Melissa Marks, Karen Matson, Robin May, Paul Mebane, Lars Nielsen,
J.W. Pieper, John Prentice, Wilt Shaw, Pete and Melissa Shepherd, Jennifer Sorrenson, Julie Strepek, Ron
Tietz, Donna Taylor and Daryl Styblo as photographer
Rookery Monitored Weekly:
February 6th through June 12th, 2018
The “Roadside” tree was the only focus of the study this year (Figure 4). Nest building activity
was not observed in other sites previously known to have had activity.
Six identified nest sites had Great Blue Heron, Ardea herodias and/or Great Egret, Ardea alba
association. Of the six nests A, B, O, S and U, where previously monitored. Nest V was the
only new nest site this year (Table 2). Nests A was not present at the beginning of the season,
thought to have been blown out of the tree by storms or high winds, but it was rebuilt slowly as
the season progressed. Nest B was for the first time ever the earliest occupied nest. It generally
has been observed that nest A is always the first occupied. Nests B, O, U, and V were occupied
consistently throughout the season and believed to have incubated young.
Five nestlings and/or fledglings were observed during one monitoring period on May 3, 2018.
Although five nestlings were observed during one monitoring event, adding the raw data high
counts per nest A (2) + B (2) + O (2) + S (1) + U (2) + V (1) yields a total of 10 nestlings.
However, all 10 were never observed at the same time. As mentioned in previous reports there is
the possibility that the high counts may inadvertently count an adult as a fledge or the fledges
where visiting another nest. Once the tree leafs out, it is sometimes very difficult to distinguish
the differences between an older fledgling and an adult. When the fledges start moving around it
is also difficult to know if they remain in the nest of origin or “visit” other nests. Lastly, there
was one sighting of a nestling noted on April 26th in nest S, however this was a singular event
and no other heron nestlings or fledglings were reported for this nest.
The team noted egrets standing in nests A and S on May 8th and in nest A on May 10th, but they
were not sighted at all after the 16th and no further activity was recorded at these nest sites the
remainder of the season. Interestingly, egrets where also noted to be in the tree on those same
dates in 2017.
The summary data from the 2018 season is presented on the following pages.
January 15, 2019 has been set as the training date for the 2019 season.
-2-
Active Nests Fledglings Date of first chick observation
Year GBHE GREG GBHE GREG GBHE GREG
2018 6 0 5 0 April 5 none
2017 8 0 11 0 March 28 none
2016 8 0 11 0 March 29 none
2015 5 4? 8-10 1 April 28 none
2014 9 1 11 2 March 18 May 20
2013 6 0 4 0 April 16 none
2012 4 0 1(2?) 0 May 22 none
Table 1. Summary statistics for Roadside Rookery
The earliest observation of adult herons in the Roadside tree occurred on 06 February 2018.
The new nest for 2018 “V” was named per the same alphabetical nomenclature adopted in 2012 and
letters A through V are now identified in the Roadside Rookery Master Nest Matrix (Table 2). The
five nests that successfully produced young were B, O, U & V. The first hatchlings were observed
in nest O on April 5, 2018 (Table 1). A singular nestling was recorded in nest V on the 8th and 15th
of May. No other observations of nestlings, fledglings or adults were recorded for nest V after those
dates.
Beginning May 8th, the young in nest “O” were referred to as fledglings as they started to venture
beyond the nests to the branches beyond. Thereafter, fledglings were consistently observed in nests
B, O, and U, with fledglings in V never being recorded.
The greatest number of birds in the tree also occurred on April 19th, week 16, when 11 herons were
counted (Figure 3).
The last recorded observation of fledglings occurred on June 12thth, week 23, when a single heron
fledge was associated with nest B. Anecdotal monitoring on the Cibolo Preserve confirmed no
further herons or egrets were at the tree on subsequent dates, so June 12th marked the end of the 2018
monitoring season.
-3-
Cibolo Preserve
Total reproduction results by year
45
39
40
35
30 27
25 24
25
20 18
14
15 11 11 11
10 8
5 5
5 2 2
0
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
Great Blue Herons Great Egrets
Figure 1. Total reproduction results from survey inception are shown.
Total Fledges compared to total number of nests
45
40
35
30
25
20
15
10
5
0
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
Great Blue Herons Great Egrets Total No. Nests
Figure 2. A comparison of total fledges to the total number of nests in the tree. Notice our
highest number of successful fledges occurred with relatively few nests in 2005, 2008, 2010 and
2011. Our lowest production in 2012 had the highest number of nests.
-4-
-5-
Figure 3. Total number of birds specific to the Roadside rookery. Weeks 16-20 are generally considered the “busy” time
in the rookery when nestlings become apparent and eventually venture out onto the branches and are referred to as
fledglings. As they leave the nests, the numbers decline progressively until the breeding season comes to a close.
Figure 4. Location of the Roadside Rookery and the associated vantage sites to view the
rookery.
-6-Roadside rookery tree = single letters; Fernbank tree = single letters Nest Official
page bottom absent Name
2012 2013 2014 2015 2016 2017 2018 2019 2020 2021
A A A A A A A
B B B B B B B
C C C
D D
E E
F F F F
G G G G G
H H
I I I I
J J J J J
K K
L L
M M M M
N N N
O O O O O O
P P P
Q Q
R R R
S S S S
T T
U U U
V V
W
X
Y
Z
A
B
C
D
E
0 5 9 14 13 8 6 0 0 0 0 Total
Table 2. Roadside Rookery Master Nest Matrix shows the nests built and identified each year
since inception of study at this tree. Once a nest site is identified the name remains with that site
even if a nest is not built there in subsequent years. See nest “C” as example. Nest established
in 2013, was not present in 2014, but appeared again in 2015.
-7-Figure 5. Master nest guide for 2018 season. Nest V was newly established in 2018.
Nest A was not present at the beginning of the season, but was subsequently re-built
in the same location as it existed in prior years.
-8-Figure 6. Photo by Daryl Styblo. March 19, 2018. Prior to
leaf-out, heron delivering stick for nest building.
Figure 7. Photo by Daryl Styblo. May 8, 2018. One of the
two dates egrets attempted to occupy the tree. Note the young
herons on bottom left.
-9-Figure 10. Photo by Daryl Styblo. March 19, 2018.
Early attempt to copulate.
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