Birders,
I observed two Least Terns at Lake Hasty today, May 16th, only one day
later than their usual arrival date of May 15th. Lake Hasty is a staging
area for Least Terns most years, but it contains no nesting habitat. In
past years, their arrival would have been no big deal, but they have
become increasingly rare as nesting species in the state, and even their
continued existence here is far from assured. They are strongly drawn to
island habitat free of terrestrial predators. From a high of 32 pairs
statewide in the 1990s, they gradually dropped to 12 nesting pairs in
2012. Enough young survived to sustain a nesting population, but nesting
was not as successful as in the 1990s, a period when island habitat
allowed the production of up to 46 fledged young in the best year.
Nesting has largely been confined to mainland nesting sites for the past
15 years, and their colonial nesting preference has meant that if
predators found one mainland nest, they often found them all.
In 2013, the population crashed. Only two pairs of Least Terns nested
statewide (both unsuccessful). By 2014, only one pair nested
(unsuccessful). 2015 was even worse. One pair hung around until June
waiting for water recede, but water rose well into July with our
historic flooding last year and, for the first time since they were
discovered nesting in the 1970s, no pairs nested in Colorado.
Floods last summer raised water levels and improved the fishery for the
minnows the birds feed on. At high water levels, multiple islands exist
offshore, and these were historic nesting areas. Habitat work controlled
the vegetation that encroached for the past 15 years, and several
islands now have suitable nesting habitat, free of both vegetation and
terrestrial predators. Least Terns finally have multiple secure places
to nest this year, but adult birds no longer come to Colorado in their
former numbers. Having even one pair back is a good sign, and hopefully,
more will follow.
If nesting ensues, I will be willing to provide the same kind of guided
access I have used to show people Piping Plovers. I don't have a problem
with people reporting them fishing on Lake Hasty, where they won't nest.
Duane Nelson
Las Animas, Bent County, CO
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