Though not the only reason for the peregrine falcon's decline, the pesticide DDT had passed through the food chain and weakened the shells of peregrine eggs, leading to the loss of many young before they could hatch.
The curtailment of chemical pesticides and the success of nest boxes like Thermal’s have led to an impressive recovery of the peregrine falcon population.
MRMC Thermal’s peregrine falcon nesting box is part of a state-wide falcon recovery program managed by biologist Greg Septon.
Read the Wisconsin Falconwatch – 2023 Nesting Season Report (PDF) (see page 17 for our nest) to learn more about Wisconsin peregrine falcon nesting activity and the young that were produced.
2023 06 12: Wings!
2023 05 26: Banding Day - Max & Snoopy
2023 05 24:
2023 05 22: 11 DAYS DIFFERENCE (5/11 & 5/22)
Only two this year. The other two eggs did not hatch.
2023 05 11 - Mom
2023 May 10 - Some hatching going on!
2023 May 5 - Four Eggs awaiting hatching
2023 April 3 - Three Eggs!
2023 March 31 - Two Eggs!
2023 March 29 - First Egg!
2023 March 21 - 1st Day of Spring!
2023 February 17
2023 February 10
Unbanded adult female observed at the Thermal Plant nest. Likely the same female who has been present the past five years.
Greg Septon's bet is that the male will continue to be Donald who has been observed throughout the winter at the MolsonCoors site and may control two territories and produce young at each site again this year. Time will tell.
About the Peregrine
Peregrines take their prey in flight, so they dine almost exclusively on other birds. However, very young falcons may catch flying insects and, occasionally, Arctic peregrines will catch and eat ground-dwelling animals like lemmings.
Male peregrines, which are substantially smaller, will generally catch smaller birds, but females will take larger prey like ducks. Peregrines can eat as much as one-quarter of their weight at one sitting.
Peregrines usually begin breeding at about 2 years of age. The male will put on an aerial courtship display to attract a mate to a selection of nesting sites. The female chooses. Peregrines generally mate for life, returning each year to the same area and even the same nest. However, the female will accept a new mate if the first is killed.
There’s nothing fancy about the nests. The nest, "scrape," is traditionally no more than a depression in a cliff ledge. But nowadays, possibly in response to increased human contact during captive breeding projects, many peregrines find homes in man-made structures and more populated areas, using power plant smokestacks, steeples, tall buildings and bridges.
Females lay a clutch of 3 to 5 eggs in the spring. The eggs range in color from pink to brownish and are about 2 inches long. It takes about a month before the eggs hatch. Newly hatched peregrines, weighing in at about 1.5 ounces, double their weight in just six days and and increase tenfold by three weeks. Hatchlings are covered with fluffy white down, replaced by feathers in 21 to 35 days. Peregrines first fly 35 to 45 days after hatching, when they have reached adult size. They begin to hunt around 60 to 80 days.
The mortality rate is very high for young peregrines. Only one in 10 makes it to breeding age. They can live for up to 15 years.
Range / Migration
Peregrines are found all over the world except in Antarctica and the Pacific Islands. The most common subspecies in the United States, falco peregrinus anatum, is found from central Alaska to central Mexico and usually winters in South America. A maritime subspecies, Peale’s peregrine, found in the Northwestern U.S. and north, does not migrate.
Generally, the birds head south in September and may spend a month to reach their winter homes in Central and South America. Arctic peregrines have been seen as far south as Argentina. Some urban peregrines do not migrate anymore, since their prey – pigeons and starlings – remain abundant year round.
Nesting Box Webcam
Through the box’s webcam, you can watch for the falcons to return, eggs to be laid and hatched and activity in the nesting box as the chicks grow during nesting season (March through July). Note that the webcam image below is not a streaming image but does refresh every 60 seconds.
Viewer discretion is advised.
Due to the sometimes-violent nature of birds of prey, some webcam content may be difficult to watch. Please be aware webcam content is not monitored or screened.