Kestrels, the smallest of falcons, are on the decline and scientists aren’t sure why

Zach Smith of High Falls with a fledgling kestrel. (Photo by Lauren Thomas)

Just a few minutes’ drive to the south of New Paltz, in the Shawangunk Grasslands National Wildlife Refuge, recently-hatched kestrels are fighting for their lives. Members of the smallest and most common falcon species in the United States, their first struggle is to compete with their nest-mates for a share of the food brought by their parents. It’s a harsh beginning, but one that sets the stage for a challenging life: many kestrels don’t survive their first year’s migration down south, and never return to these traditional nesting grounds to mate.

Zach Smith, an independent raptor biologist who studies kestrels, is pleased with the number that have hatched thus far this year. “We have eight active nest boxes, all with young,” he said. “Most will probably fledge.” Five of the boxes being used are in the grasslands, with the other three on private land.

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Nest boxes, installed on poles ranging from eight to 15 feet in height, are a solution Smith and other scientists are trying to address for a decline in the kestrel population nationwide. Whenever an animal species population falls, one factor is a loss of habitat, and for kestrels the most delicate part of their habitat needs arise during mating season. Hunting anything from grasshoppers to mice to sparrows, kestrels nest in the cavities created in trees by the loss of a branch or other malformation. They want to be high enough above the ground to feel their young won’t be eaten by land animals, and near the fields where they do most of their hunting.

High intensity land use such as farming tends to wipe out ideal nesting grounds for kestrels, Smith and other biologists believe, and nest boxes have been introduced both to give them a leg up, and allow scientists to take a peak into their secret domestic lives. As with many falcons, a disturbed nest likely means no young this year, which is why they don’t tend to thrive near high levels of human activity. With his training and experience, Smith can check in on local nesting kestrels often enough to see how they’re doing while not disrupting their lives, but making the wrong move might result in parents never returning to feed their young.

Smith has been doing this work for over 20 years, and kestrels in particular have become “a passion and obsession” for him. “Kestrels are one of the most common raptors, but they’re in decline and we’re not sure why. It’s a cause for concern.” A lot can go wrong in a raptor’s life: lack of food, lack of hunting skill, bad luck and being eaten by bigger birds are among the natural challenges; humans pose issues of their own ranging from removing habitat to spreading pesticides to wind power, which is generated by blades up to 70 feet long that can move at 170 mph, slicing any bird unlucky enough to fly into the path to ribbons. There’s also competition from starlings, an invasive bird species aggressive enough to take up all the prime nesting spots.

The boxes set up in the grasslands are very well received. Part of that is because Smith does his best to clear out any starlings who set up housekeeping within, but the wildlife refuge also has abundant prey for these small hunters. They need to collect a tremendous amount of food during their time as parents.

Kestrels mate for the season, and may hook up with the same mate in subsequent years. Males arrive first and establish territories, and then females assess their potential mate’s ability to provide for a clutch of young. Once mating occurs, the female will lay an average of five eggs, one every other day. They’re only about an inch long, tan with a brown speckling on the shell. The female sits on them for up to a month, with brief spells by the male to eat what he’s hunted.

Other than relieving his mate two or three times a day, the male hunts and keeps an eye out for predators during this time. Once the eggs hatch, things get a bit more harried for both parents, because once the chicks grow enough feathers to thermoregulate their own bodies, both adults must focus on hunting to feed their insatiable maws. At two weeks old, the only parental contact the young get is likely to be a fly-by to drop off more meat to eat.

Fledging happens close to five weeks. The young will start poking their heads out first, and their parents coax them into the light, showing them how to fly and, soon thereafter, demonstrate how to hunt. The young stay close for a couple of weeks after fledging, and can depend upon their parents’ hunting skills for a month or two after leaving the nest.

“The first fall and winter are the hardest,” Smith said, and up to 80% of young kestrels don’t survive the challenges of learning to hunt for oneself while migrating to their winter grounds, which for kestrels in the eastern U.S. will be in southern states, or at least states south of New York. “Hunting is not an easy lifestyle.”

Those that do return often are unable to secure mates, which is perhaps a good thing; failed nests are often the result. Older, more experienced kestrels have mastered their hunting skills and also built up body fat that can make them sustain lean years better.

“Sometimes, I’m overwhelmed with respect for these birds,” Smith said. In comparison, “We are so feeble.”

While visitors to the Shawangunk Grasslands National Wildlife Refuge may be fortunate enough to see kestrels, Smith notes that they are a protected species, which means that neither they nor their nests may be disturbed. Take only pictures, and leave only footprints.

There are 2 comments

  1. FunkieGunkie

    Maybe the decline has to with the exponential increase in tourism that the government encourages. Every time a new parcel gets “protected” it is no longer private property but “public lands” that are used for all sorts of recreation by people from every corner of the Tristate area. Www.mohonk.info

  2. Mary K

    There is a 75% decline in insects over the last few decades due to pesticide use and habitat loss. Since insects are close to the bottom of the food chain this affects pretty much every bird and mammal.
    The Moth Snowstorm by Michael McCarthy (2016)
    https://www.nyrb.com/products/the-moth-snowstorm

    One recent study
    https://www-m.cnn.com/2017/10/19/europe/insect-decline-germany/index.html

    Help reverse this by planting native plants and buying organic food. Ask your state to use native plants for Highway and other public projects.

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