Big, hooved animals help little falcons at Spring Mills farms

By STEVE EISENHOUSER

SPRING MILLS — Four years ago, two falcon nest boxes were installed on Windermere Farm owned by the Allebach family in Spring Mills. Within weeks, the smallest falcon — the American kestrel — moved into both boxes to lay eggs and, two months later, produce seven new falcons to fly off and make their own way in the world.

Each subsequent year kestrels have produced at least one brood in the Allebach nest boxes. Thanks to the big, Percheron horses on the farm, the surrounding grazing land has areas of low and medium height grasses that provide habitat for innumerable small rodents and large insects for kestrels to eat. Over the ensuing four years, similar nest boxes were installed on nearby livestock farms.

This year, 15 boxes on nine Spring Mills-area livestock farms produced 65 kestrel young.

The American kestrel, previously called a sparrow hawk, has been in serious decline in the northeast states, with decline estimates as high as 85 percent in the past 50 years. Possible reasons for the decline vary from loss of habitat (grazing land and grassland), pesticide issues, an increase in Cooper’s hawks that prey on kestrels and a lack of suitable tree cavities for their nests.

Properly-mounted and constructed nest boxes have proven to increase kestrel numbers. In Pennsylvania, kestrel nest box programs were first initiated 60 years ago, and at least one — at the Hawk Mountain Sanctuary — has been in continuous operation since then.

In 2016, a central Pennsylvania program was initiated through assistance from Penn State’s Shaver’s Creek Environmental Center. In 2021, nest boxes on 31 Centre County farms (including the nine Spring Mills farms) produced 195 kestrel young that were banded and, hopefully, will help further expand the population next year.

The Central Pennsylvania Conservancy, a nonprofit land trust based in Carlisle, now sponsors the kestrel nest box program that produced 48 kestrel young in 2016 and 480 in 2021 in the 5-county central Pennsylvania study area. There are 87 farms in this area currently participating.

Almost all participating farms have horses, cattle or sheep, or are adjacent to farms with livestock. Livestock and kestrels work well together. Hoofed animals stomp on shallow mice and vole tunnels, bringing the small rodents to the surface where kestrels can reach them and livestock graze grass to levels where kestrel prey is more visible. In return, kestrels help keep rodent, grasshopper and other insect levels down.

The kestrel nest box program is volunteer staffed with a licensed bander to apply bands, maintain records and closely supervise any assistants handling birds during the banding process. Although some people believe that handling nestling birds can cause adults to abandon them, decades of research have shown this is not true.

Subsequent band recoveries from discovery of dead or injured birds, or from scientific trapping efforts, provide much valuable information about kestrel migration, life spans and behavior. Each aluminum band has a unique number stamped on it and a website address for reporting band recoveries.

Most kestrels in the area migrate south in winter, returning north in the spring, almost always choosing a different mate. Most nest boxes are reoccupied each year, but not by the same pair. Some of the kestrels overwinter here, in which case kestrel pairs may stay together in consecutive years.

Kestrels are colorful birds, but their small size — about the size of a robin or mourning dove — makes them difficult to identify until you become familiar with their characteristic flight pattern, tendency to hover into the wind while feeding, and tail-bobbing while sitting on a utility wire. They are the country’s smallest falcon species, and only weigh about 4 ounces as adults. Females are larger and heavier than males, but the difference is typically only about 10 percent more in size and weight.

Anyone with significant areas of grassland or grazing land who is interested in having a kestrel box on their land should email Steve Eisenhauer at steveeisenhauer0@gmail.com. The property can then be evaluated to see if the habitat is suitable for kestrels and if it is close to our kestrel nest box trail route.

Steve Eisenhauer is regional director of protection and Land Stewardship, Natural Lands, Peek Preserve, Millville, N.J.