Feathers and Preening

You have probably never thought much about feathers unless you raise chickens and wind up plucking them yourself. Or your duvet is full of down and feathers and you find them all over the place if there is a small hole. But, maybe, like many of us, you wish you had wings and could fly – like Icarus – but not with the same consequences. I wish I had feathers and wings because then I would soar into the sky as high as I could go!

Before I begin, this posting is not the definitive answer to everything about feathers or preening. But I hope to give you a glimpse into the importance of both to Red-tail hawks. Sort of a nutshell version. If you are really interested in feathers and believe me, there is a lot to learn, I have included the name of a good book later in this blog.

Red-tail hawk chicks begin to jump and flap in the nest, according to my observations, approximately 2-3 weeks after they hatch. They are building the muscles in their wings when they flap and flap. Flight feathers not only help birds fly and soar but they are contoured and offer protection from the weather. In the first photo below, there is a snow and ice storm in Ithaca on May 8. Big Red’s feathers are keeping her dry and also protecting the chicks. Look carefully at the one under her beautiful red tail feathers.

Feathers keep birds warm and dry – in ice, rain, and snow. The chicks have not yet developed feathers to do this so Big Red covers them.

Several times this spring, the rain has just been torrential in Ithaca. Again, the feathers kept Big Red, no matter how drenched she looked, dry and in turn, she spreads her wings to keep the chicks dry and warm.

For us newbies, we were worried about Big Red in all the rainy weather. Here she is covering the chicks. They get so warm that they often stick their heads out just to get cool. And just a note. Both Big Red and Arthur have brood patches where their feathers have worn down from incubating the eggs and then protecting the chicks.

When it is really hot and humid as it is in both Ithaca and Syracuse the last few days, rain can be very welcome to hot hawks. Below is an image from the Syracuse University Hawk cam showing two of their newly fledged red-tails dancing in the rain to cool off. It reminds me of being in India in the late 1980s and 1990s. You would beg for the rains to come to cool off and would run out into the rain ever so thankful!

So remember. Flight feathers are not just for flying but they are also for protection from the weather. The water resistance from the feathers comes from hydrostatic pressure. Hydrostatic pressure is the tension between the structure of the feather versus the pressure of the water. Water droplets bead on the feathers.

Arthur leaving to get prey for the chicks with Big Red giving him directions. Notice his legs tucked up and the slight curve of his wings at the end and, of course, that beautiful red tail.

Wing feathers are the longest and the most useful for flying. Below is a closeup of one of the chicks with their wing feathers starting to grow. Also notice the tail feathers that are beginning on the chick and the recognizable “red tail” of the Red Tail Hawk on Big Red. The chicks will not get their beautiful red tails until they are in their second year. Tail feathers are like the rudder on a boat. They help the birds manoeuvre. About a month after they have fledged, the chicks should be able to soar into the sky.

Approximately 18% of the weight of a Red-tail Hawk comes from feathers. By the time the chicks are 29-31 days old, their dorsal wings should be 90% feathered. Their legs will begin to feather and they will get the characteristic “pantaloons”. The ear openings should be covered and the upper tail coverts should be well developed. By the time they are 35 days old (about a week from a possible fledging or first flight off the nest), the head will be at least 50% feathered, the dorsal body will be 95% feathered, and the breast should be 90% feathered. Their tail feathers should be five to six bands long, preferably. The more bands the more successful the first flight will be.

This chick is J3, the youngest. He is 31 days old. Note the distinctive “peach” on the breast, the lovely dark feathers marking the “apron” below the crop. The downy head is beginning to gets its feathers and the feathers covering the legs are there.

At the time these chicks fledge, their wing and tail feathers will be longer than their parents. With their first molt, they will return to normal. Molting is the falling out and gradual replacement of the feathers.

There is a really good book on feathers. It is Feathers: the evolution of a modern miracle by Thor Hansen. There is so much to learn including every part and its function! Apparently humans have the DNA to grow feathers but we don’t have the “switch” to turn it on and off. Feathers are much more efficient than their hair. Hawks also use their feathers like a sharpening tool to keep their beaks in perfect condition.

The simple definition of preening is that it is cleaning and maintaining the feathers. Preening reinforces and conditions the surface of the feathers with gland oils. These gland oils contain vitamin D. When the feathers are exposed to sunlight after preening, the oil works as a protective conditioner. The oil in the glands change composition during the year just like you will, if you live in a cold climate in the winter, change the weight of your oil in your car. Red-tail hawks spend approximately 77% of their time preening.

This is an example of a warble. This is when the head of the bird is folded all the way back and down and they are preening their wings
The chicks learn quickly how to balance themselves on branches or metal railings and preen at the same time!

One of the things that I found most interesting about the feathers is that because they are hollow, some researchers understand that birds can feel the changes in barometric pressure and will know what weather conditions are approaching. They are more likely to know the precise weather approaching than the local weather station. They have to. They live outside in the trees, roost on the ledges of buildings, and depend on millions of years of evolution to give them clues to nature’s mysteries so they can survive.

Why are female Red-tail Hawks almost always 30% larger than the males?

It is called Reverse Sex-size diamorphism. There are several theories as to why this happens with Red-Tail Hawks.

The first is that the females had to be larger to protect themselves from the feisty males.

The second is that the females selected smaller males to be their mates because the size difference allows each of them to hunt different prey and reduce any competition for food between the pair. Raptors that hunt birds are generally smaller and faster with the female specializing on larger prey. At the beginning of the nesting season, the female becomes an active hunter and again when the nestlings are larger. Generally the adults tend to partition the prey resources in their territory.

Another theory is that the females need to be larger because they must accumulate reserves in order to produce eggs. When they are incubating eggs and brooding young, they rely on the male to feed the family. Red-tail hawks are usually born in April when the prey are sluggish and just coming out of hibernation. Small males can make quick turns. In the case of the Red-tails on the Cornell Campus, Arthur W, the male, is known as the ‘stealth bullet.’ He is quick, fast, focused, and quiet when he hunts. Big Red’s former mate, Ezra, was like Arthur W a great hunter but he was also about 30% smaller than Big Red as is Arthur.

Ezra has his wings spread and his legs tucked tight. If you look closely you will see that he is delivering two items to Big Red. The first is a snake and the second is a flower!
It is very difficult to get Big Red and Arthur to stand up straight at the same time. They certainly do not listen to requests from humans!This is the closest I have come to finding an image that might be able to show you the difference in their size. Big Red is on the left and has her head leaning back preening and she is a little more slumped than Arthur who is on the right.

In terms of the nestlings, the only way to positively known the gender of the bird is through either a DNA sample or you see them laying an egg when they are older. Everyone likes to guess the sex of the chicks growing in the nest cup. Using reverse sex-size diamorphism, we speculation whois a female by their overall size as they grow in the nest and the size of their feet. But again, no one can be absolutely sure. In the past one of the small nestlings was always believed to be a male. This particular bird injured its wing and, as a result, had to be taken to a vet. The bird’s DNA was tested and, to the surprise of many, it was determined to be a female. So not every small Red-tail Hawk is a male!

In terms of the relative size of each J, J1 is the largest of the three. Early in its development, everyone noticed the large size of its feet. Now as a juvenile, J1 remains the largest of the three siblings. But there is something else about J1 that I personally find fascinating. J1 is very much interested in nest maintenance. She can be seen, even today, mimicking Big Red in attempts to vent the nest bowl. She rearranges the nest twigs and on the second day after she fledged, she brought a branch to the top of the Rice patio. There seems to be 100% agreement that J1 is going to be a good mama like her mother, Big Red.

J3 in the front and J1 behind watching J2 fledge. Look at the difference in the size of their legs as a starting point.

J2 on the other hand is also a large bird, not as large as J1 but larger than J3. J2 was actually the first egg to be laid but the second to hatch and is, therefore, actually the oldest. His fledge was more like a fludge when he climbed up on the light box and then slipped but his flight was still remarkable. J2 has continued to be a very, very strong flyer already interested in hunting. The shape of “his” head – you will notice that I continue to use the term “his” – is also different than that of J1. He has an intense focus and besides bugs and insects he has already been interested in small birds in the territory. To my knowledge he has not caught one. He is also very aggressive. A few of us believe he is truly a male and will be a great hunter like his dad, Arthur W.

J3 eating his first prey drop after fledging.

J3 is the problem child that everyone loves. . J3 was born four days after the other two and it was also the last egg to be laid. Taken together, J3 is actually a week younger than its siblings. That is a lot in the life of a Red-Tail Hawk chick. It may also account for the fact that Arthur W brings food to the nest tower in an apparent effort to feed J3 away from the two larger siblings. Let me try to explain what has been happening. Normally the juveniles are spread out being individuals. This trio is quite different according to the people who have monitored all of the broods on camera (since 2012). It is because they tend to congregate together. To hang out. If one is on the Rice patio, all three might be there.

All three on what is called the Rice patio. Arthur W often makes food drops here but it is also a safe and flat site where they can sleep in the sun or practice their skills.

They might all be on one of the towers including the nest tower. Still, on occasion, they go their separate ways.

J1 in one of the oak trees near the Fernow Building looking at a squirrel.

A prey drop is just that – one of the parents dropping lunch. The juveniles will, unless they have recently eaten, fight for the food with the most aggressive mantling the prey. Unless the prey item is too large for the chick to eat all at once, sharing doesn’t seem to happen. So, because of J3s size and a seemingly lack of aggressiveness in comparison to J2, J3 is somewhat at a disadvantage. This is the reason that I believe Arthur W still supplies food on the nest to the little guy.

Arthur has been dropping lunch off to J3 for several days now. This was around 3pm. He seems to be looking for J3 who arrives almost immediately.
J3 mantling the prey that Arthur W dropped on the nest. Remember mantling is a way of protecting the food item so that no one else can steal it.
J3 finishing up his afternoon snack.

For now, the gender of the three juveniles is sheer speculation. There are no banding practices and no GPS monitors on the Js. In other words, no identification. It is only when one of the juveniles might find its way to the vet and be both recognized and tested that the sex would be determined.

Tomorrow we are going to talk about the importance of preening.