Final Report to the
For the 8th
consecutive year, endangered and threatened water-bird species were monitored
from spring arrival dates to fledging dates for those nesting in the
Nesting site protocols were changed for 2016 and continued in 2017 due to the increasing numbers of nesting pairs of Forster's and Common Terns, to minimize human disturbance at the two sites.
April 29: With a cold
and rainy spring water levels were very high. Returning Forster's Terns found
their nesting site at
May 16: Very high water levels continued and Forster's Terns began to disperse to other areas of the state, with about 100 adults loafing in the eastern marsh and a few attempting to nest on old muskrat huts. Common Terns began to arrive but no evidence of nesting was found.
May 30: A check of
June 1: I surveyed two Black Tern Colony sites on the west end of the lake with very discouraging results. Only one pair was found at a site that had 12 nests in 2014. The second site and no nests. This site had 6 nests in 2014. I then surveyed 3 other sites on the west end with much better results with 12 nests total which was similar to 2014. I then checked two colony sites on the east end and found 14 adults with 7 nests, down from a count of 34 adults and 17 nests in 2014. However, I found a new colony nearby that had 8 adults and 4 nests. These could have been birds the split from the other two colonies surveyed in 2014. But even with these birds included, the east count was still down significantly.
June 2: Only four
days after surveying the tern rafts, I decided to check on the Common Tern
situation. Warmer weather and south winds caused the Dunlins and Turnstones to
head north and the Common Terns began to nest in earnest. Raft #1 had 31 adults
with 10 nests and 20 eggs, while Raft #2 had 28 adults with 6 nests and 14 eggs.
Water levels at
June 12: Common
Tern Raft #1 now had 17 nests with 36 eggs and 3 additional nest scrapes. Raft
#2 had 13 nests with 31 eggs and 3 scrapes. A total count of adult Common Terns
was 55. Forster's Terns were nesting on
July 7: Raft #1
now has 24 chicks and 3 nests with 6 eggs. Raft #2 has 22 chicks and 3 nests
with 7 eggs. These were estimates as chicks were running everywhere. So as not
to disturb the chicks which varied in age from one-day-old to 10 days old, I
did not enter the rafts for a more complete count. I checked
July 12: I returned with avian ecologist Sumner Matteson to band the Common Tern chicks. We banded 26 chicks on Raft #1 and counted 11 eggs. We then banded 31 chicks on Raft #2 and counted 15 eggs, for a total of 57 chicks banded and 26 eggs remaining to hatch. Since 13 of these eggs had been laid in only the past 5 days, we suspected nest failures had caused these birds to do a re-nest. Although encouraged by 26 eggs, we expected a low hatch rate at such a late date.
July 28: Only 7
of the 11eggs on Raft #1 had hatched with 7 un-banded chicks observed. There was also 3 nests with 2 eggs each, but only one of them was
being incubated. All of the previously abandoned chicks had fledged with many
of them loafing and being fed by adults on the Dredgebank.
Raft #2 had one banded chick, but no hatchlings were observed and no eggs were
present. I suspected egg loss had occurred due to gale force winds rolling the
eggs to the far end of the raft. I then
found 18 fledged Forster's Terns on
Aug. 1: Matteson and I returned to band the 7 chicks on Raft #1, but only 6 chicks were found. To our surprise however, we found two very small chicks on Raft #2. Evidently there was a nest with two eggs that was hidden in the vegetation that hatched since July 28. There was also a nest with two warm eggs on Raft #2. We suspected a failure would occur for this nest but I would check in a couple of weeks to make sure.
Aug. 25: I checked Raft #2 and found two large chicks that were being fed by their parents and guarded by other adults. Matteson drove up and we banded the two chicks. We also counted 16 Caspian Terns on the Dredgebank.
Summary: In spite of a late start,
gale-force winds and predation by Turnstones, nesting success on the two Common
Tern rafts proved very successful with the banding of 67 chicks making
Recommendations: The Common Tern raft project should continue. Based on an almost even split in nest numbers on both rafts, it appears that Common Tern pairs have pretty much maxed out the rafts. The only way to increase production would be to add an additional raft which can be added to the existing site area.
Forster's Terns will return to their historic site at
Although Black Tern nest numbers dropped from 2014, there is
plenty of nesting habitat available for these birds. Predation is more of an
issue with Black Terns than with Forster's or Common Terns since they nest in
areas vulnerable to mink and raccoons. That said, they
more easily adjust to fluctuating water levels than Forster's Terns using
several varieties of habitat. Management projects for Black Terns have shown
mixed results. But decreasing numbers over the past four years at
As always, I would like to thank the LPPRD for their partnership in these programs over these many years and hope that it will continue to do so into the future.
Water bird monitor, 2017