It seems that the Rochester Falconcam has entered the Twilight Zone. Overnight, one of Mariah’s eggs vanished. A careful review of the images from the cameras didn’t yield any clues as to what might have happened. The only thing we know for sure is that yesterday there were five eggs, and today there are only four.

The Rochester Falconcam team used Camera 1’s ability to pan and tilt to search the catwalk area just below the nest box. We were looking for shell fragments or any other indication that the egg might have been pushed out of the nest, but despite a detailed survey we found nothing. That leaves us to speculate as to the egg’s fate.

It is possible that the egg was damaged while it was being turned by one of the falcons. You’ll recall that falcons turn the eggs during incubation to ensure even heating of the egg. Earlier this year at a Peregrine nest in Ohio, one of the eggs was broken, so it’s possible that might have happened here too. If that’s the case, the most likely explanation for its absence is that she ate the egg, or what remained of it. The egg shell is a valuable source of calcium, and Peregrines often eat the shells after their young have hatched.

Some readers have wondered if Mariah might have discarded it because she realized it wasn’t viable. That’s unlikely. Peregrines, including Mariah, have been known to incubate eggs that turned out to be nonviable, even long after the other eggs in the clutch had hatched. Also, during reintroduction efforts, Peregrines’ eggs would often be taken for artificial incubation and “dummy” eggs put in their place. In those cases the falcons continued to brood the fake eggs as if they were real.

Even though we didn’t see any evidence of an egg when searching with our camera, it is still possible that it was ejected from the nest, either accidentally or on purpose. The camera has a couple of blind spots caused by objects that block the camera’s view of the catwalk, and the egg could be hiding behind one of those. Also, the weather may have played a role. If the egg was dropped onto the catwalk, the high winds at the top of the tower may have moved it out of camera range, or even blown it off the catwalk entirely.

The only way to learn more would be to make a visit to the nest box in person, and we won’t do that. Mariah is in the middle of brooding her eggs, and we don’t want to disturb her, certainly not for the sake of satisfying our curiosity. Unless there is some great calamity, no one will venture anywhere near the nest box until the eyases are removed to be banded in early June. Meanwhile, we’ll have to settle for speculation, and hope that the remaining eggs go on to hatch successfully.

-Jess

Look carefully at the group of eggs– there are two on the right, one behind the other, for a total of five!

Mariah continues to surprise us all this year! Sometime around 4:00 PM today, she laid the fifth egg of 2007, about 67 hours after her previous one. Since she laid the first egg on March 26, they’ve come at intervals of 50, 106, 60 and 76 hours respectively– an average laying period of 73 hours, or about 20 hours more than her normal 54 hour intervals, so she has us all completely flummoxed this time around.

Here’s another shot…

Four eggs are lined up in front, with the fifth egg hidden behind the second one (counting from the left). Mariah’s breast and the eggs in front make it hard to see, but if you take a close look you can just make it out.

Mariah’s been incubating the eggs for the past five days. Usually, Peregrines begin incubating when the next to last, or penultimate egg is laid. They do this to ensure that all of the eggs will develop together, and hatch at more or less the same time. With the fifth egg being laid five days after the third, it’s likely that it will hatch after the others. That may put the last eyas at a bit of a disadvantage since its other siblings will be bigger and stronger, but there’s probably no need to worry about that. Mariah has had other “late” eggs in past years and even the smallest of her offspring usually end up being just fine. One of the major reasons for that is because Kaver has proven to be a very good provider, even for the large broods that Mariah seems to like. He’ll certainly be busy with five hungry eyases to feed (to say nothing of feeding himself and Mariah), but he’s an old hand at it, and an excellent hunter, so we’re confident that he can repeat his performance of years past.

I suppose the question of a sixth egg is appropriate. Mariah laid six last year, so it’s possible, and with her newfound unpredictability it would be foolish to think she’s done even now. We’ll see in a few days whether she’s going to surprise us again.

-Jess

It looks like Mariah was laying this egg at the same time I posted my last article! How’s that for timing?

You can click the small image at the left for another view. Careful observers of the cameras, especially Camera 2 (a night vision model), noticed that Mariah frequently changed her position within the scrape last night beginning around 8:15 PM local time. She settled down about five minutes later. That kind of restlessness is often associated with egg laying, so even though the first view of the egg wasn’t available until early this morning, we believe she actaully laid egg #4 around 8:20 PM on the 4th of April. As you can imagine, we’re all very excited here at the Rochester Falconcam!

Will there be a fifth egg? We’ll know in a few days…

In the meantime, here’s a great illustration of a brooding shift change (click the image to see the full-sized version). You can see Mariah “encouraging” Kaver to leave the eggs so that she can brood them. She does this by using a vocalization called a “wail”, which tells Kaver that she wants to take a turn on the eggs! You can read more about that in my article on incubation.

-Jess

Who can say? If Mariah were sticking to her “traditional” egg-laying schedule, we would have expected to see another one sometime in the afternoon. She is still looking fluffed up and even a little gravid, so it’s possible that she has another egg on the way. Since she’s clearly not keeping to her old pace, we’ll just have to wait and see.

I’ve consulted with some falcon experts and learned a couple of things. The first is that long egg-laying times are not quite as rare as the literature might seem to indicate. It happened at a couple of nests in Toronto, Canada, for example. In those cases, territorial disputes appear to have been the cause, but age, weather and external stresses can all cause egg laying to be delayed. The consensus seems to be that as female Peregrines get older the normal gap of 48 to 72 hours between eggs can stretch, sometimes quite a bit.

It is possible that Mariah laid an egg between the second and third ones that we see in the nest box. We don’t know of any alternate nest sites in the area though. Also, since laying the third egg (and even before) she has been exhibiting typical brooding behavior at the Kodak nest site. She’s also been here almost constantly, so if she did lay an egg elsewhere, it has almost certainly been abandoned.

In fact, Mariah and Kaver have both been spending a lot of time incubating the three eggs in the nest. The picture at the left, from earlier today, shows Kaver arriving at the nest to take over brooding from Mariah. In true falcon style though, Mariah has been doing most of the work, with Kaver taking over only for a couple of hours at a time. When he’s not taking his turn incubating the eggs, he stays near the nest. Usually he’s perched just outside the nest box.

This is a typical pose for Kaver when he’s brooding the eggs. Notice how he’s leaning a bit forward, with his tail up in the air? He sits that way so that he can get the brood patches on his breast in contact with the eggs. It’s the extra heat from the brood patches that causes the eggs to develop. If he just pressed his abdomen against the eggs he wouldn’t transfer enough heat for incubation to continue. So his posture is a clue to what’s going on in the nest.

So, keep your eyes on the Rochester Falconcam! Maybe Mariah’s on track to lay another egg, or maybe we’ll just have three this year. We’ll just have to keep watching and waiting for now.

-Jess

Yes, that’s right my friend, THREE EGGS!

Wow, am I ever glad I hedged my bets in my previous article. Mariah has never gone this long between eggs, but that’s what’s great about watching these falcons– they always show you something new.

I’ll see what I can learn about such a long period between eggs, and share what I find with you when I do!

Specto Subitus! (Expect the Unexpected!)

-Jess

Remember in a recent article I said to expect the unexpected when watching falcons? Well, here’s another example.

When we talked about egg laying, I noted that Mariah had never laid fewer than four eggs since she and Kaver became a pair in 2002. It seems that there’s a first time for everything, though. Mariah has begun brooding, or incubating the two eggs she has laid. A Peregrine usually begins brooding when the penultimate egg is laid, but remember that Mariah usually lays her eggs about 54 hours apart. This year, her two eggs were laid 50 hours apart– a bit shorter than normal for her. It’s been more than 80 hours since she laid the second egg. Scientists have seen examples of eggs being laid more than 72 hours apart, but it’s very rare. We never say never here at the Rochester Falconcam (it kind of goes along with expecting the unexpected), but at this point it looks like Mariah’s done laying eggs for this year.

You’re probably out there yelling at your computer screen right now, “How do you know Mariah’s incubating the eggs, Jess?!?”

Well, that’s a good question, so thanks for asking! We know she’s begun brooding by watching her behavior. During incubation, one of the falcons will stay on the eggs almost full time. They only take short breaks, leaving the eggs uncovered for a few minutes. In an eight hour period today, the eggs were only left uncovered three times, for no more than three minutes each time. That means for more than 98% of the time the eggs have been covered. Since it’s not very cold outside today, it’s pretty clear that they’re actually incubating, not just protecting the eggs from chilly air.

As we discussed before, Mariah and Kaver take turns brooding the eggs. Mariah incubates about 2/3 of the time, often for four or more hours before Kaver relieves her. Males brood for shorter periods– typically 2 to 3 hours, and they brood less frequently. While one adult is brooding, the other may be out hunting. Brooding falcons still need to eat, after all. If they’re not hunting, the other falcon usually stays close to the nest. Sometimes while Mariah is brooding the eggs Kaver will bring her food that he has hunted. She’ll eat the food outside the nest while he takes a turn incubating, but then she’ll come back and take over– provided she can get him to move off the eggs. If he doesn’t move right away, she may stand in the nest box and wail at him. Wailing has different meanings for falcons, but in general it indicates dissatisfaction with the current situation. So if Mariah wails at Kaver while he’s incubating, it’s her way of telling him she’s not happy that he’s still sitting on the eggs. As with most other interactions between male and female Peregrines, Mariah usually gets her way, though sometimes it takes a while for him to get the message.

So, just how does incubation work?

Heat makes the eggs start developing. When the eggs reach about 98.6°F, or 37°C the egg begins changing into an eyas. Conveniently enough, a Peregrine’s natural body temperature is about 103°F, or 39.5°C, so to heat up the eggs all they need to do is to get some of that body heat onto the eggs. Now, a Peregrine’s feathers make very good insulation. That’s how they can stand to stay out in cold temperatures without freezing to death. But while those feathers keep the cold air away from the falcon’s skin, they also keep their body heat from getting out. So to incubate the eggs, the Peregrine carefully settles down, shifting from side to side to get the eggs beneath their feathers. Falcons have brood patches, areas on their breasts with a lot of blood vessels close to the surface of their skin. The blood vessels concentrate their body heat, making it easier to transfer the heat to the eggs. Both Mariah and Kaver have brood patches, though his are smaller than hers, which makes sense since he’s a smaller bird (if you’ve been following along with Imprints you’ll know why. If not, go back and read about sexual dimorphism in Falcon Identification 101).

Peregrines incubate their eggs for 33 to 35 days. In the early days of brooding it’s important to keep the eggs as close to their ideal incubating temperature as possible. Too hot or too cool and the eggs won’t develop properly. Later in the incubation process, proper temperature isn’t quite as important. In fact, after a couple of weeks the falcons will be able to leave the eggs uncovered for longer periods of time. Sometimes leaving the eggs uncovered frequently, or for long periods can mean that the eggs hatch a few days later than normal. That usually doesn’t happen with Mariah and Kaver, though. Their nest box is in a place where it’s not likely to be disturbed, so they most often incubate steadily until the eggs hatch.

If you watch closely, you might see Mariah or Kaver get up, move around, then settle back down on the eggs. Sometimes they do this just to get into a different position, and maybe to give their legs a bit of a stretch, but often what they’re doing is turning the eggs. They turn the eggs to ensure that they get evenly heated. If the eggs aren’t heated evenly they may not develop, or they may develop abnormally. It’s also possible for the developing egg to stick to the inside of the eggshell. Turning the eggs keeps the egg membrane from sticking to the sides of the shell. Falcons turn the eggs using their bills and their feet. As you can imagine, they turn their eggs very carefully! If you’re watchful and lucky, you may get to see a picture of them turning the eggs. It may look like they’re stepping on the eggs or pecking at them, but now you know what’s really going on.

-Jess

The colder weather in Rochester over the past few days has encouraged Mariah and Kaver to spend some time keeping the eggs warm. Don’t confuse this with incubation, though. Right now, they’re just keeping the eggs from freezing. Mariah and Kaver do this by sitting over the eggs to keep the cold air away. That’s what Mariah’s doing in the picture at the left (click it to see a larger image)

A falcon’s eggs are like any bird’s, with an outer shell for protection, a yolk inside the shell which acts as a source of nutrition for the developing embryo, albumen (a clear fluid that acts as the embryo’s water supply while it’s developing), and of course, the embryo itself. The intense heat of incubation is what starts the process of turning those components into an eyas (if you’ve forgotten what an eyas is, you can find out here). For now, Mariah just needs to keep the eggs from freezing.

Kaver can keep the eggs warm too. In fact, Kaver seems to enjoy egg sitting duty. Sometimes he enjoys it so much that Mariah has to stand over him for quite a while before he gives her a turn!

Still, Kaver spends most of his time outside the nest box, either hunting for food or defending his territory. Over the past few days he’s driven out several intruders– Hawks, mostly– that came too close to the nest. Yesterday was a bit more exciting. He chased away another male Peregrine that wandered into the territory. Local falcon watchers reported that Kaver and the intruder took turns diving at each other until the stranger left the area. Those kind of confrontations aren’t that unusual, especially during the springtime when birds, including many species of raptors, are migrating. Rochester lies on a major migration route for birds in North America, so Kaver will have plenty of migrants to drive away in the coming weeks.

– Jess

At about 10:40PM (EDT) Mariah laid her second egg. Here’s a picture shortly after the event:

That’s a bit sooner than her average egg-laying rate of about 54 hours, coming just a bit more than 50 hours after her first, but no one at the Rochester Falconcam is complaining!

-Jess

I was all set to write an article about the behavioral changes we’d see as Mariah prepares to lay her eggs, but she skunked me, and laid her first egg before I was ready! That’s a lesson for us all– when watching these falcons, expect the unexpected.

Now that she’s laid her first egg, let’s talk about what we can expect from Mariah over the coming days. Since Kaver arrived on the scene in 2002 Mariah has never laid fewer than four eggs. In 2003, 2004 & 2005, Mariah laid five eggs and all fifteen of those eyases (the name for falcon chicks) survived to fledge– that is, to take their first flights. That was a record in New York State.

Last year Mariah laid 6 eggs! She suffered an injury to one of her legs right around the time they began hatching, and her reduced movement hindered her ability to care for the eggs and her new chicks. As a result, only three eyases survived, but all of them went on to be remarkable fliers.

Mariah with eggs in 2002

How many eggs can we expect this year? It’s always hard to say, but if the past years are any indication, it should be at least four. We’ll know for sure in a few more days. Peregrines lay an egg about every two days. Mariah takes things a little slower than the average Peregrine, laying an egg every 53 hours, give or take an hour or two.

Between eggs, her behavior is that of an expectant mom– she’s lethargic, and she’ll spend a lot of time near the nest, if not actually inside the nest box. She may also have a fluffed-up appearance, or even look unkempt, with her feathers all askew. It’s the Peregrine equivalent of a bad hair day. As the picture at the left shows, she may also look heavy, or gravid as the eggs form inside her.

Once fertilization occurs the egg begins moving down her oviduct. It’s sort of on an assembly line where the egg gets built, layer by layer. First comes several coatings of yolk. The egg moves a little farther down the ovidicut where it gets covered with albumen (the clear fluid that we’d call egg white) and various membranes. Then it continues on its way until shortly before she’s ready to lay the egg, it gets its final layer, the shell. The whole process takes a little more than a day.

The actual act of laying the eggs can take as little as a few minutes or as long as an hour or more. When she’s ready to lay her egg, Mariah will sit in the scrape. She may look like she’s sleeping, or at least taking a nap, but if you watch carefully, you’ll notice that she starts to move around as the egg is laid. She typically keeps the egg covered after it’s laid for 10 to 20 minutes before moving off the nest and letting us have a good look.

Peregrine eggs are speckled, and vary in color from light pink to darker brown or purple. Older falcons may produce lighter colored eggs. Each one is about the size of a small chicken egg.

One bit of behavior that many people find unusual is that she won’t begin incubating the eggs, or brooding, right away. Believe it or not, that’s perfectly normal for Peregrines. She’ll begin brooding when the next to last egg is laid, so when she starts, we can be pretty sure we know how many eggs she’ll lay– just add one to the current number. Before then, she’ll mostly leave the eggs uncovered. Don’t worry though– Peregrine eggs can survive just fine unless the temperature drops below freezing. If that happens, she’ll sit on the eggs just to keep them warm enough to stay viable. We’ll talk more about brooding and incubation soon. In the meantime, keep watching!

-Jess

The Rochester Falconcam is very happy to announce that Mariah laid her first egg of the 2007 season just after 8:00PM tonight! Here’s the first clear picture from the Rochester Falconcam’s infrared camera, taken at 8:23PM:

Mother and egg appear to be doing just fine! We’re all very excited to see how many eggs she’s going to lay this year. Watch for more information about Peregrine egg-laying behavior in an upcoming article.

-Jess