More gratuitous learning to fly shots

So I couldn’t just leave it at the pictures. Here’s one way that these birds build up their flight muscles.

Learning to fly

Ok, I’ll count this post as gratuitous bird stuff.  Part of it does stem from a question I get a lot: “how do birds learn to fly?”  Well, they learn by doing.  The most important piece of it, though, is getting their muscles ready for the stress of flight.  As a result, all birds spent a lot of time in the nest working out those big muscle groups before they ever take to the air.   Once they take off and leave the nest, they’re on their own. So why gratuitous?  Because in order to answer this question about flying, I was able to get some pictures of those young Peregrine Falcons doing some of this practice.  This balcony near the nest seems like an ideal place for a young bird to get some experience.

You can also see that most of their baby feathers have been molted.  They’re nearly ready to take off!

Here comes the rain again

As we prepare for another day of rain in Charlotte, I keep getting questions (many from my mother) about how the falcons handle the rain.  I can’t imagine that they really love it, but it really doesn’t do them much harm right now.  Feather are really quite good at insulating the birds from the water.  If they’re on screen during a storm, you can usually see birds fluff themselves up.  When a bird does that, it’s actually repositioning its feathers so that they hold more air close to the body and keep the water off of them.  Unless the rain goes on for days (or the feathers are unhealthy or the birds are full of parasites), then they can stay pretty dry under there.

In fact, it looks like the rains are actually probably pretty good for these birds, since they’re not stuck in the nest anymore.  Peregrines rear broods more successfully in years with plenty of rain during the nestling season.  If there’s too much rain during the incubation part of the year, that’s a problem because it can result in a wet nest which can make incubation more difficult.  The wet nestling season should be good for producing lots of insects, which is good for producing lots of healthy birds who make for good dinner for the falcons.

Olsen, P.D. and J. Olsen.  1989 Breeding of the Peregrine Falcon Falco peregrinus.  III.  Weather, nest quality and breeding success.  Emu 89:  6-14.

Right now, their feathers look pretty good, if a bit messy.  You can see the  their juvenile plumage coming through the bits of down still left on their bodies, here.  This photo is one my mother took today.  The adults are just out of the frame, on the rail above the kids (making all sorts of noise, apparently).

Pretty soon, those birds will be ready to take off into the world.  Are they looking off at the world or watching the impending storm?  Or possibly singing a Eurythmics tune?  That’d be my bet.

 

 

The Girl is Mine

Walking through the neighborhood this afternoon, I had my attention drawn to a high-pitched burbling sound.  Across the street from me were three Brown-headed Cowbirds.  They were walking through a yard, foraging in the wet grass and occasionally picking up some food (a worm or larva or something- I couldn’t tell at that distance).  The fascinating thing about watching this group of cowbirds moving along was that it was a group of two males and one female.

Now Brown-headed Cowbirds are brood parasites, which means that they lay their eggs in the nests of other birds and do not provide any parental care at all.  As a result, this group was not a family group of birds.  It couldn’t be.  Once a female cowbird drops her eggs off in the nest of some other bird, she’s done.  In fact, she may lay as many as 40 eggs in a single breeding season in nests that range over an area as large as 450 hectares (1100 acres or 1.7 square miles).

Scott, D.M. and C.D. Ankney.  1980.  Fecundity of the Brown-headed Cowbird in southern Ontario.  Auk 97:  677-683.

Rothstein, S.I.; J. Verner; and E. Stevens. 1984.  Radio-tracking confirms a unique diurnal pattern of spatial occurrence in the parasitic Brown-headed Cowbird.  Ecology 65:  77-88.

Well, if it’s not a family group, then who were those three birds?  One of the clues came from watching the behavior of one of the males.  He stayed between the female and the other male the whole time I watched him and he was the one making the high-pitched vocalizations.  In fact, each time that he vocalized, he lowered his head, raised his tail, spread his wings and aimed himself directly at the other male.  He was displaying  and mate guarding.   Even though cowbirds are not particularly good parents, they do appear to be devoted partners.   In most populations, they do seem to be mostly monogamous.

Yokel, D.A.  1989.  Intrasexual aggression and the mating behavior of Brown-headed Cowbirds:  Their relation to population densities and sex ratios.  Condor 91:  43-51.

So if these birds are monogamous and mate guard, what was that third male doing hanging around?  In the time that I watched the group, he didn’t make any moves to get closer to the female, nor did he respond to the vocalizations of the calling male.  He just kept plodding along, following the other two birds through the grass.  Well, one idea that could explain this male’s behavior stems from the fact that these birds never get to interact with their parents in the nest (the whole brood parasite thing).  If you never get to see what your parents do, then how can you learn how to court and woo a mate yourself?  Apparently, the answer to this question is to find someone else to watch.  Male cowbirds who hang around older, adult males and pairs have a higher reproductive success later in life than males who spend less time around other adults.  So in order to be successful and to learn how to do his own mate guarding, he’s got to spend time watching someone else do it.

Freeberg, T.M.  1999.  Spatial associations provide a context for social learning of courtship patterns in Brown-headed Cowbirds (Molothrus ater).  Journal of Comparative Psychology 113:  327-332.

So in the end, that female had a quite vocal male declaring his ardor for her and trying to drive the other male away.  It reminded me a lot of that old Michael Jackson/Paul McCartney song, which is probably a good model for what the young male had to learn.  Sing like these two and you shouldn’t have any problems with courtship next season.

 

All the noise noise noise noise

One of the questions that I was asked was about how the noise from uptown events (like the NASCAR Speed Street event) would affect the behaviors of the Peregrines on their nest.  In general, living in a place like the one they chose on the 40th floor should have prepared those birds for dealing with the sights and sounds of the city, already.  As I looked around, though, I found that other people have examined the effects of noise on these birds more specifically.   If jet plane noise doesn’t have much of an effect on parental behaviors, then a bit of NASCAR shouldn’t have too much of an effect.

Palmer, A.C.; D.L. Nordmeyer; and D.D. Roby.  2003.  Effects of jet aircraft overflights on parental care of peregrine falcons.  Wildlife Society Bulletin 31:  499-509.

Interestingly, the pattern that they found in these birds affected by jet engines was that males spent less time at the nest and females spent even more time at the nest- during the incubation periods.  Apparently, there was no affect of noise on the provisioning rates of the birds.  Given that the chicks are still looking pretty good, I’d say that our nestlings handled that stress pretty well!

 

An afternoon workout

I’ve been out of town for most of the past few weeks and have missed a lot of the growing up that these birds have been doing.  I opened up the website today to see one of the chicks doing a bit of a workout, stretching and flapping its wings- a very important activity for a bird that’s going to be flying soon.  Those pectorals are big muscles that need to be ready to do some work!!  Even though I can’t see Mom and Dad on the nest, they’re clearly doing their job bringing food back to the chicks.  There’s quite a bit of variability in just who brings back food to the nest, but in general, males are the ones who supply most of the food in Peregrines.

Olsen, P.;  V. Doyle; and M. Boulet.  1998. Variation in male provisioning in relation to brood size of Peregrine Falcons Falco peregrinus.  Emu 98:  297-304.

Now here’s where the next few weeks will get interesting.  Once the birds leave the nest (when the chicks fledge), we won’t likely see them there again.  Mom and Dad may return next season for another go-round, but the chicks are likely to take off.  The family will probably stay together for a period of time, but just how long is hard to say.  In Osprey, fledged young may remain dependent on their parents for 30 or so days after leaving the nest.

Bustamente, J.  1995.  The duration of post-fledging dependence period of Ospreys Pandion haliaetus at Loch Garten, Scotland.  Bird Study 42:  31-36. 

In contrast, Lesser Kestrels only take care of their young for about 5 days after the young fledge.

Bustamente, J. and J.J. Negro.  1994.  The post-fledging dependence period in the Lesser Kestrel Falcon naumanni.  Journal of Raptor Research.  28:  158-163.  

In any case, that means that all of these chicks really have to get good at being on their own very quickly.  Once they leave the nest, they don’t have much time at all to get good at taking care of themselves.  So keep watching the workouts!

Sibling rivalry (again)

Clearly, I’m in a title rut, now.  I’m willing to keep running with this theme, though, because there’s so many fun things going on right now.  Last week I was over at a friend’s house.  Sitting in his backyard, I noticed a pair of American Robins that were clearly flying to a nest on one of the supports over his deck.  When the parents flew off, I walked over to take a quick peek at the nest and saw five young robins sitting in the nest, heads pointed up, squeaking and jostling around in the nest.

Now all that movement is kind of fascinating.  First of all, it meant that they weren’t hiding from me (not surprising, since they were on someone’s deck, already.  They should have been used to seeing people- and dogs – moving around below them).  Secondly, the parents had been making multiple feeding trips back and forth.  Since they were both off the nest at that moment, they were likely to return again, soon.  So that meant that these kids could have been jockeying for better positions in the nest.

It turns out that American Robin chicks are quite adept at this kind of positioning behavior.  One group of researchers in Canada put video recorders near American Robin nests and tracked the movement of the kids in the nest with respect to where the parents landed to feed them.  Two things stick out from what they found.  First, parents tended to return to the same spot on the nest to begin feeding.  Secondly, the chicks were sensitive to that pattern and would fight to get into the best position. It’s sort of like watching people waiting outside Target on the day after Thanksgiving.  Everyone just sorts of tries to work towards the front to be the first one in.

McRae, S.B.; P.J. Weatherhead; and R. Montgomerie.  1993.  American robin nestlings compete by jockeying for position.  Behavioral Ecology and Sociobiology 33:  101-106.

As a result, there isn’t really a true hierarchy.  No one individual is the most dominant, they all just sort of take turns being the ‘pusher’.  At least that’s true when there’s plenty of food to go around.  When food is scarce, well, some of those chicks may not survive because they’re not good enough at doing that pushing- and that would usually be the last ones who are born.  Like the Peregrine Falcons, American Robins don’t lay all their eggs at once.  One article from 1898  (and here’s my little aside for today:  if you’re never read old science, do it!  It’s so different and fun!)  puts the interval at 24 hours, but there is likely some variability with that.

Howe, R.H.H.  1898.  Breeding habits of the American Robin (Merula migratorius).  Auk 15:  162-167.

So in a good year, all that sibling rivalry is just good-natured fun.  In a bad year, that rivalry affects which of those birds will survive (and the youngest ones are likely to be the losers in that situation). Being the youngest child in my family, I’m very sensitive to that kind of situation!!

If you’re keeping an eye on the Peregrine Falcons nesting in Charlotte (FalCam), then keep this sort of competition in mind and keep answering these questions:

1.  What kind of food are the chicks getting?

2.  Which of the chicks eats first?

3.  Which of the chicks eats more?

Now get to work!