Egg-laying is just around the corner for our peregrine falcons! The earliest layers – Dairyland Power Genoa is usually among them – tend to begin in late March, although egg-laying can continue into late May at some of our nests! We don’t know when the new, as yet unnamed female will lay eggs, but Michelle usually started in late March or early April, with laying coming a little later in cold, dry years. Given all the drama at GSB, I thought this would be a good time to talk about peregrine falcons. We’ll start with the basics!
What’s Going on At Great Spirit Bluff?
Watchers know that female falcon Michelle has not yet returned to Great Spirit Bluff. It is unlikely she will do so at this point: we have pairs back at almost all of our nests and egg-laying is just around the corner. Newman has been seen courting an unbanded female and, very briefly, Karen 44/P, a 2016 hatch from Minnesota Power’s Clay Boswell nest box.
Like bald eagles, peregrine falcons were long considered to be monogamous. It’s more or less true if your idea of monogamy includes deadly mate competitions, winner take all! As we’ve seen this year, Newman is more than happy to welcome new female falcons in the absence of Michelle. As we saw last year, Newman was quite happy to welcome Michelle back, even though she chased the falcon he was already courting away. Bob believed that peregrine falcons were bonded first to place and secondly to mates – completely in line with what we see at all of our nests.
Polygyny has been documented in peregrine falcons, but it is fairly rare. They do not appear to engage in extra-pair copulations, aka promiscuous mating in monogamous species or, as some of you call it, cheating.
The Peregrine is the fastest animal in the world, diving or stooping at speeds that can reach over 200 miles per hour. Almost everything about it is built for speed, from the baffles in its nose to the jagged edges of its slim, stiff feathers and long, pointed wings.
The falcon catches other birds in flight by diving on them from above. As she begins her stoop, she rolls, cups her wings around her body, and tucks in her feet. This change in shape streamlines her profile, yielding an aerodynamic raindrop that can cut through the air at high speeds.
As she plummets, her nictitating membrane protects her eyes from dust and debris in the air and a secretory gland helps keep her corneas from drying up. A special cone or baffle in her nose regulates the amount of air entering her nasal cavity, allowing her to breathe and protecting her from damage. A curved flight path keeps her prey in view and allows her to respond to last-minute escape attempts without losing lift. Before she strikes her prey, she’ll experience G-Forces estimated at between 25-27 Gs.
The peregrine meets her prey feet-first. She slows first, unfurling her wings and tail, and dropping her feet. After striking and stunning or killing it outright, she’ll loop around in mid-air to retrieve it and take it to a safe place for plucking and eating.
Lifestyles of the Fast and Furious
Falcons are roughly crow-sized. Females are about a third larger than males, although they both have blu-ish to slate grey backs, barred or streaked white to rusty underparts, and a dark hood. Adults have black beaks and yellow feet, although their babies may initially have bluish feet. This is natural and not a cause for alarm.
Both males and females are highly territorial. We believe that they are fairly solitary birds even off their nesting grounds, although groups of young peregrines have been reported on oil platforms and ships in the Gulf of Mexico. I would love to see more studies on their ‘wandering years’ and wintering grounds. We know very little about their behavior off-territory.
Traditionally, Peregrine falcons nest on cliffs, laying their eggs directly on a scrape they created in a gravel or sandy substrate. In the Midwest, Peregrine falcons generally:
- Lay eggs in late March or early April
- Hatch in late April to early May, or 33 days after the first egg is laid.
- Begin flying in mid-June or later, or about 40 days after hatch.
Peregrines are excellent, attentive parents. The babies cannot thermoregulate (control their temperature) until they are about 10 days old, so Mom spends a great deal of time huddling over them while Dad feeds everyone. As the babies age, both parents spend time hunting. The eyrie is small and the babies, which have among the fastest growth rates in the animal kingdom, are large and hungry. They eat, sleep, poop, and go from white fuzzballs to sleek brown juveniles in 38-40 days.
Once they begin flying, young peregrines spend a lot of learning how to fly and hunt: something that looks a lot like play to most human observers. Their parents will continue to provide some food for their newly fledged young who are not yet self-sufficient. Come fall, the adults may or may not migrate, but their children will disperse between mid-July and early September. Once they are gone, they are gone. If they do come back to the nest, their parents will defend it from them.
What to expect when falcons are expecting
You can watch for peregrine falcon courtship at any of our nests, although Great Spirit Bluff is my favorite! Watch for fancy flying (the male or tiercel falcon flies acrobatically, sometimes wiggling his tail as he goes), bowing, scraping, and incredible fly-in copulations. Males will gift females with food, and both sexes will work on a scrape, digging into the gravel with their breasts and pushing with their legs to create a depression into which the female will lay her eggs. Falcons do not create tree nests, although they have been documented laying eggs in unused Bald Eagle nests.
Female falcons will begin laying three to four reddish speckled eggs sometime in late March or early April. Peregrine falcons do not begin full incubation until after egg number three is laid, so it is normal for them to spend time – even quite a bit of time, depending on how warm it is – away from eggs number one and two. Eggs should begin hatching roughly 33 days after the third egg is laid.
During incubation, falcons experience hormonal changes that help keep them incubating. They may appear sleepy or lethargic as they pick at gravel and sit on their eggs. Females do most of the incubation, although their mates will spell them briefly during the day. Smaller males sometimes have a harder time covering all of the eggs, depending how many are laid. We can also expect to see egg rolling and some shimmying. This is not a particularly active time for the falcons: Bob used to refer to incubation as the ‘egg doldrums’.