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Seasonal Summary for Cub Creek Heronry
- To: Carolinabirds <Carolinabirds@duke.edu>
- Subject: Seasonal Summary for Cub Creek Heronry
- From: Alan Johnston <alanj46@yahoo.com>
- Date: Mon, 8 Jul 2002 09:41:53 -0700 (PDT)
- Sender: carolinabirds-owner@acpub.duke.edu
On Sunday morning, July 7th, I checked the Great Blue
Heron colony at Cub Creek, which flows into the
northwestern end of Jordan Lake. Most of the nests
are now empty, but I still counted 19 young herons
standing on their nests, and 5 or 6 adults flying in
and out. The dozen Black Vultures present on my last
two visits had now disappeared.
Here is a summary of my sightings at the colony this
season. Between March 14th and July 7th I made eight
trips to the heronry, mapping the nests each time and
making a note of how many adults or young were visible
standing or sitting on each nest. The totals for the
year included 63 nests, approximately 94 adult herons,
and 132 baby herons.
During the season I mapped a total of 63 nests.
Adults were seen standing or sitting on 59 of the
nests at one time or other. Baby or young herons were
counted on 41 of the nests. My best estimate is that
approximately 94 adult herons were involved in this
colony. Although the maximum number of adults counted
at any one time was 58, if you assume each adult is
associated with a specific nest, I was able over time
to count 82 adults standing or sitting on a specific
nest, and an additional 12 adults associated with
specific trees where I could not see a nest. For each
nest I added the maximum number of young herons seen
at the nest at one time. At 3 nests I saw only 1 baby
or young heron. At 4 nests I saw two young herons.
At 17 nests there were three young; 15 nests had four
young; and two nests, both at the very top branches of
a tree, had five young. These nests got very crowded
and noisy as the babies grew at 8 to 10 weeks into
almost full size juvenile herons. A total of at least
132 baby herons hatched at this heronry this year.
During the course of the eight visits to the site I
only saw one dead baby heron, which had fallen out of
a nest and gotten hung up in the branches below. But
I assume the vultures were there for a reason. But
short of spending much more time out at the site, I
can not think of an efficient way to estimate how many
juveniles survive and fledge. Ehrlich (1988) gives a
fledging time of 56 to 60 days. Several juveniles in
this colony were still at their nests 63 days after
hatching. I welcome suggestions on monitoring this
site, and look forward to visiting it again next
season. I will be glad to provide specific directions
to the site.
Alan Johnston
Chapel Hill, NC
alanj46@yahoo.com
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