Monday, May 30, 2011

And now the brown pelican

From my weekend at the rookeries, I have spent a fair amount of time learning more about snowy egrets, great white egrets and cattle egrets (see previous 3 posts). Now, my attention again turns to the brown pelican. Following these birds for the past 3 years has been the highlight of my rookery photography. As much as I enjoy the egrets, it is the brown pelican that has consistently provided photographs and I enjoy watching them for hours at a time.

When I first arrived at the rookery this morning, it was barely 7 am and the sun was casting a golden light. This is a time of day for photography that I love but also find more challenging from a canoe. I do not like to use an ISO setting greater than 800, so this leaves me with no more than a 1/500 shutter speed at f5.6 when photographing the brown pelicans. I can get away with a much fast shutter speed with white birds. But during the early minutes of the morning, it is the brown pelican that I find to be most photogenic. They like to swim and fly early in the morning, so I often come up on the rookery noticing several immature and adult pelicans flying in to the rookery islands or swimming around the area. I was also fortunate to have an east wind, which meant that the birds would be making their flight landings while facing me, as seen in the photo above.

The slow shutter speed is fast enough to capture these birds sharply but also with some wing blur, which I like. Here is another photo. Sadly, the bird is missing a foot.

Soon after, I paddled closer to one of the islands which was mainly inhabited by pelican nests. There are a few nests that are low enough to be almost eye level. I can kneel in my boat while shooting, which provides me a 1- 1.5 ft higher perspective than sitting. And today, I had an incoming tide which meant that the water level would quickly raise up. Perfect for rookery photography. A few weeks ago, I blogged on the brood reduction hypothesis so noticeable among the brown pelicans. Here are a couple photos that clearly demonstrate the size difference within a brood. Notice the two smaller pelicans behind the big one in the first photo. In the second photo, the smaller sibling's face can be barely seen against the bigger bird's wing near the mangrove leaves.

While focusing on some egret nests, I noticed a pelican scene in an island about 100 ft away. At the top of the mangrove canopy, a couple pelican chicks were beginning to receive some food from a parent. The scene was beautiful with all birds mostly cleared of branches. The way the parent and babies were fluttering their wings, I had a wide horizontal shot and actually had to zoom out to 330-360 mm to avoid cutting off a wing, which you can see I did in the first photo.

Here is one photo after the feeding with the adult poised to take off, leaving its chicks to wait for the next meal.

Later in the morning, still focusing on egrets, I noticed an adult pelican flying into the water and swimming under the mangrove roots to pick out a branch and then fly it back to its nest in a nearby island. I paddled a bit closer as it was side lighted. By now, the sun was quite high and the lighting a bit severe. Here's a couple shots of the adult with some nest material.

I am not sure if I will be back to the pelican rookery again this year. I am content with that; it's been a very good season and everyday that I can visit the rookery is a good experience. My learning curve is still relatively steep in terms of bird photography; but as I live in paradise, I will continue to have many more learning opportunities while capturing the wonder of birds.

The snowy egret

Memorial weekend provided me quality time at the rookeries. I spent the first day on Biscayne Bay (see the previous post titled "Cosmopolitan bird") and the second day at the pelican rookery in the Everglades (see previous post titled "The great white egret"). During other visits to the rookery, I have watched several snowy egrets and rarely got an opportunity to photograph them. First, they are very shy, they hide well and their flight pattern changes to avoid an intruder. Second, their nests sit low inside the tangled mangrove branches where they cannot be seen well. And third, there are fewer of them compared to the pelicans and great white egrets. So capturing a snowy egret nest scene has been impossible. In my three years visiting this rookery, I've captured one shot of a snowy flying in with a twig in its mouth, the closest I have come to photographing a nesting behavior. And only once have I witnessed a snowy adult feeding its babies. Unfortunately, I could barely see what was happening over the mangroves and certainly not well enough to photograph.

I keep trying to photograph these yellow-slippered birds, graceful in their flight. They tend to fight amongst themselves and sometimes this is demonstrated with crest raising, a beautiful display of feathers. The snowy egret is a very fierce defender of its nest and the surrounding area. I watched one or two of the adults stand alert in a fairly high position on the mangroves and call out frequently with a sharp squacking tone, I suspect a warning to the other birds to stay away. But again, capturing any of this is so difficult, sometimes because of poor lighting and most often because everything gets in the way.

Today, I had a bit more luck with these birds. One thing they do often is forage around the muddy ground along the mangrove roots. If I am lucky enough, one will walk itself into good light removed from the shadows of the mangroves. Here's one shot, although the bird decided to stand alert as it felt exposed.

There were a concentrated number of snowys in one end of an island that is about 6 ft from the end of a second island. This was a challenging location to photograph a bird with lots of shadows and busy background and foreground. I managed a few flight shots but no interaction between birds. Notice the great white egret chick looking up, a frequent posture for those birds as they wait for mom to come back with food.

There were a couple juvenile birds in one particular spot. One was brave and stood out among the mangroves well enough to photograph. My first thought was that this was a juvy snowy egret; after all, it was among adult snowy egrets. Later, I was speaking with Jason, one of the eco tour guides in the Everglades and he thought it was a reddish egret. If it was, that would be quite a remarkable find. So I did some investigating when I got home. I found my answer in the Stokes field guide to birds book.

Reddish egret - all black bill
Snowy egret - bright yellow facial skin at base of bill clearly distinguishes it from the similar immature little blue heron
Little blue heron - gray facial skin at base of the bill clearly distinguishes it from the similar snowy egret

Here are a couple photos of the bird. What do you think? Definitely a snowy egret!

If I ever get a good shot of a snowy egret, I consider myself lucky. Generally, I do not see many snowy egrets close enough to photograph on Biscayne Bay or out here in the Everglades. Once, I sat for an hour in my boat near a lone snowy egret on Biscayne Bay. It was so intent on fishing that it barely took notice of me, only 10-15 ft away. Another time I was on Florida Bay in front of the Flamingo marina where a large mud flat was covered with birds. There were several dozen snowy egrets wading around; a one time event for me. What was so fun about this scene were the equal number of laughing gulls that would chase the snowy egret after it worked to capture a bait fish. In flight, one or more gulls would try to gang up on the snowy and steal its booty. Here is a photo from each of those lucky moments.

The great white egret

Along side the brown pelican nests are the great white egret nests. This year, I had a difficult time following these guys during my visits. The biggest difference between the pelicans and the egrets is that the egrets have much lower tolerance for intruders. My rookery rule is to get no closer than 50 ft from the edge of the mangroves (for the bird's comfort as well as to get a better shooting angle with a 400mm capacity). With some wind or current, I increase that distance because of the difficulty in getting my boat positioned properly. Staking out and/or anchoring while minimizing my disturbance is a test in patience and sometimes impossible. Today was not so bad and I was able to use the stake out pole (much easier to deal with than the anchor). Inevitably, the white birds become nervous as I approach, while the pelicans appear calm and unwavered. Consequently, I've remained farther away from them and have concentrated on the more accessible pelican nests.

Today however, the egrets were more visible in the nice front light. One reason is that the chicks have grown and are more easily spotted. This imposes yet another challenge and that is to get clean shots of birds that mingle with so many other birds. Nevertheless, I was able to focus on a few egret nests where 1 or 2 chicks lived while the adults flew in and out for feeding and other chick caring responsibilities.

Watching an adult egret feed its young is fascinating but not easy. The pelican feeding is quite unruly, but what makes the egret feeding so much more painful to watch is that the birds have very sharp beaks. This cannot be a pleasant experience for any involved. The adult must avoid getting a chick beak in its eye and in fact, I noticed one adult that appeared to have an injury possibly from an impalement. In the meantime, with 2 or more chicks fighting for food, they must also avoid getting impaled. From my observations, the chick clamps its beak onto the adult's beak, unlike the cormorant and pelican chick that is allowed to put its entire head and neck inside the adult's throat. For obvious reasons, the sharp beaked egret cannot let that happen.

The feeding ritual goes something like this. The adult flies in while the chicks jab vigorously at the sky. The adult stands tall for several seconds while the chicks stretch upward attempting to get to the adult's mouth. After a short time, one of the chicks manages to clamp onto the adult's beak and without warning, the adult bends down as each of the chicks attempts to get the regurgitated food out of its mouth. This lasts for several seconds and then the adult stands tall again. It stretches its long neck and points its beak straight up and holds this position for a minute or so. Then, the feeding begins again. I am guessing that the adult is doing this stretch to move the regurgitated food back up into its mouth.

After feeding, the adult manages to get away and looks relieved when doing so. After one chick was fed, I focused on it as it flapped its wings, obviously irritated that the parent had left it again. With these egret scenes, I went back and forth between horizontal and vertical shots. While focusing on this one young chick, I held the camera horizontally in attempt to capture its wings. What I realized afterwards is that a vertical shot would have rendered a much better shot. Case in point, look at the first photo below. A vertical frame would clearly have captured the wings in their entirety. Once again, I missed my shot. The next one is not bad and I was glad to have captured the scene with the right exposure and sharpness.

Like the pelican, survival rate among GWE chicks is as low as 25% during the first year of life. While the pelican chicks require 4-5 mon before reaching independence, the GWE chicks are on their own in 2-3 mon. Chick competition in the nest is fierce. The adult lays its first egg and will continue laying up to 6 eggs with 2-3 days between each egg laying. This is amazing to me because chick growth is fast and in theory (my theory) the preceding chicks could outsize the new chicks substantially. However, whenever I observe a GWE brood, the 2 or 3 surviving chicks appear similar in size. In contrast, the 2 or 3 pelican chicks within a brood vary noticeably in size despite only hours between hatches. The GWE lays about twice as many eggs as the pelican. My theory is that competition among the egret chicks is so great during the initial period that less than half survive, resulting in 1 to 3 strong chicks to continue growing. The smaller and weaker pelican may be able to hold on longer and continue growing for some time, possibly surviving the long haul. Growth of the GWE chick is so fast that they often look as large as the adults. Notice the similar size of the adult and chick in the first photo below.

Enjoy these photos of the absolutely great white eget.

Sunday, May 29, 2011

Cosmopolitan bird

I have sort of an affection for the little cattle egret. It lacks the grace and elegance of the great white egret, it looks like a chicken when it struts around looking for bugs to eat and it hangs out with livestock. I would never consider using the word cosmopolitan to describe the cattle egret; I associate that description with sophisticated, worldly persons, not birds that can be found just about anywhere in the world. But in that latter sense, the cattle egret is truly cosmopolitan. And I really like this bird.

Originally from Africa, the cattle egret came to North America in the 1940s. Now, they are found everywhere, including Alaska. In Florida, nesting locations are seen in most areas ranging from the panhandle to the keys. It is interesting to me that the landlubber cattle egret often chooses to nest on coastal islands along with wader birds that consume marine food. The cattle egret does not fish and rarely wades in water; rather it lives primarily on insects (lots of grasshoppers). Contrary to this, I have seen cattle egrets while paddling in the salty waters of the Everglades. Recently, there were two of them hanging out with terns and other shorebirds on Little Pavilion Key, a small spit of sand in the Ten Thousand Islands region. I've also have seen a few at the brown pelican rookery I frequent, also in the Ten Thousand Islands.

My affection for the cattle egret (species identified as bubulcus ibis) began four years ago when I unexpectedly found a cattle egret rookery on Biscayne Bay. Since then, I have observed and photographed the birds of this rookery while learning many things about them. I've observed the bird's work ethic as it maintains a healthy nest and raises 3 to 4 chicks and does so in a very short period of time. Incubation takes only about 3 weeks, chicks grow rapidly and within a week or two, can regulate their own temperature and are fully feathered by 3 weeks following hatching. They begin climbing out of the nest at about 2 weeks of age and are fully independent at 6-7 weeks. The cattle egret nests along side the cormorant, which also grow quickly, but appears to rely on mom and dad for a longer period of time, compared to the cattle egret.

With breeding, nesting and raising fast growing chicks, the adult cattle egret must work very hard. While the female tends to the chicks, the male is constantly looking for nest material. The first time I photographed the rookery I noticed how specific each bird was with its flight pattern. Within a 30-min span of time, one cattle egret can fly in and out of its nest over ten times. It was at this rookery where I began to spend quality time practicing flight shots. I've improved my ability to capture birds in flight and I have the little cattle egret to thank for that.
On this memorial weekend holiday, I arrive at the rookery early in the morning with a high tide. Given the location, I would need to use my anchor with water as deep as 10 feet. I was fairly well protected from the wind, but had an outgoing current. Once I anchored correctly, my boat was quite steady and I was able to stay in one or two spots during the couple hours I spent here.

The egrets share there rookery island with cormorants and tricolor herons, but they outnumber the other bird species easily 10 to one. There was much flight activity but not very many chicks in sight. Perhaps it is too early for them to leave their nests and begin climbing around the mangrove branches. Soon though, the babies will be climbing around the canopies of the mangroves and flying about, circling earnestly around the rookery islands as they test their newly formed feathered wings. They are more difficult to capture in flight than the adults that come and go in a straight line for the most part. The chicks learn to fly by banking sharply and circling around the rookery in an unpredictable manner. I try to track them with my lens but they are very fast and are quite aware of the intruder and will quickly turn away once I am sited.

For today, I concentrated on the adults. Enjoy these photos of the beautiful cattle egret.

Friday, May 20, 2011

Biscayne favorites

I have my favorite places to photograph. One of them is on Biscayne Bay near Matheson Hammock. From the launch site south, there is about a mile-long unhindered shoreline guarded by several small red mangrove trees that have spread out into the water. If I am not photographing birds, I am photographing the mangroves. At low tide, this area becomes a feeding ground for egrets (great whites and snowys), herons (tricolor, green, great blue, little blue) and white ibis. Low tide at 7 am, was right where I wanted it to be. The east winds were brisk somewhere between 10-15 knots and when I did not see a single bird upon arriving near the mouth of the creek, I thought I might paddle south a few miles to the hidden lake where a cormorant rookery sits. I was not wanting to paddle much distance with the winds, but with no wading birds around, it seemed to be the best alternative. I continued paddling and felt letdown to not even see a flock of ibis flying over. I paddled past the creek another 1/4 mile or so and all of a sudden, the birds appeared.

This was not going to be easy. The birds have endless space and can stay away from me without compromising their breakfast opportunities. The low tide grasses made it difficult for me to approach and I could only hope for one or two brave birds to feed where the grass meets the water. Often, I get my boat into shallow ground where I can only move if I push off with my paddle. If the birds decide to move away, I am stuck and have to push myself out before I can paddle over to the birds. It's painstaking sometimes, but today, the birds were relatively cooperative. I approached slowly while the sun eventually rose above the morning clouds. Once the sun came out, the white birds began to glow in the grasses of Biscayne Bay. I noticed a couple snowys but they never got close enough to be more than specks. Most of the white birds were juvenile little blue herons.

Little blue herons are quite common in this particular area; typically if I see one I see a half dozen or more. They are generally not too shy and often allow me to get close enough. Today, most of them were juvys, still mostly white feathered. During its first year, the juvy little blue begins its life all white and gradually turns blue in a calico kind of way. It takes about 1 year before the white-blue juvy turns completely blue. The little blue heron is the only heron that changes feather colors in such a dramatic way.

Some white ibises were about, but not as many as I usually see. My experience is that these birds begin to appear in greater number in this area towards mid to late summer. I think they are still nesting right now. I enjoy photographing white ibises, especially the beautifully patterned juveniles. The juvy ibis is similar to the little blue heron in that its feathers turn from brown to white, giving it a speckled brown and white appearance (see first photo above). But, they lack the aqua blue eyes of the adult white ibis. For the ibis, foraging is all about touch and not sight. This is one reason I like photographing these birds because they move their beaks around the water constantly. This makes for very nice poses and reflections that go well with the mangrove scenery. I follow an ibis with my continuous auto focus as it moves around the water, poking its peak in and around the grassy waters and frequently pulls out a crab or crayfish. I wait for the right moment to rifle off a few shots as the bird quickly captures its prey. The heron, on the other hand is a sight feeder. The little blue heron, unlike the great blues moves around constantly and is quite busy at feeding by moving its neck sideways back and forth before jabbing the water. It's feeding technique makes this bird one of my favorites to photograph. Once it hones in on its prey, you can be certain that the next move will be a precise jab at the water and the bird will almost always pull something out of the water.

The incoming tide rolled in quickly, which was good for me. I can bring my boat closer to the birds. After about 2 hours, most of the birds had moved toward the shoreline. As the tide moved in, I stayed with a juvy white ibis that was working a mangrove tree, looking for food among the oyster encrusted roots.

A tricolor heron flew in near the shoreline and with the sun now at a steep 45 degree angle, I followed the bird around for about 20 min. A couple great white egrets worked the shoreline and I captured a late morning shot of one of them. The mangrove roots compliment the birds that stand with their curvey long necks.

Not a bad morning at all. What am I saying? It can never be a bad morning on Biscayne Bay. Soon, the creeks will contain my favorite non-bird subject, the golden silk spider. Today, there were none, too early in the year for the females to be seen with their large webs that cross high over the creeks. In the meantime, I will try to get back to the pelican rookery in the Everglades and see how those babies are doing.

Monday, May 16, 2011

The Brood Reduction Hypothesis

Hypotheses are created from observations. Field ornithologists have a hypothesis concerning brown pelican nestling survival rates. It is referred to as the brood reduction hypothesis. Anyone with at least a small sense of bird behavior knows and is usually horrified that the smallest, weakest nestling does not survive and often dies from sibling bullying. Or as the experts describe it: "starvation, aggression and/or expulsion".

If I am going to go out of my way to paddle a canoe to areas where birds roost, loaf, breed, feed, and grow and develop, than I am obliged to learn as much as I can about them. With my observations of these pelicans for the past 3 years, I have many questions. These have led me to research brown pelican nesting and from that, I have learned a few things. I didn't expect to see only beauty and joy in nature when I signed on for this amateur pursuit of bird watching and photography. But dang if nature doesn't get more harsh and often times cruel as I learn and observe more of it.

Here's what I have learned so far. Brown pelicans of the gulf coast began breeding sometime around February. The span of time is about 4 1/2 months, beginning with 2 weeks of courtship and nesting followed by 1 month of incubation. It takes about 3-4 mon before the nestlings fledge and are no longer dependent on the adults. The breeding season varies and is greatly affected by temperature (last year's freeze delayed the season noticeably). It also appears that brown pelicans are smart enough to avoid hurricane season, enough so that the young pelicans are well fledged before a big blow.

Nestbuilding continues during incubation and after hatching. Here is a shot from mid-March this year showing a parent bringing in nest material while the other parent incubates. Both males and females incubate the eggs. Nest building is quite vigorous during this period. However, I've noticed less stick delivery going on after the hatchlings arrive.

During the first 3 months of breeding season, most of the eggs have been laid, but egg laying can continue for another 3 months. Adaptive brood reduction is the name of the game for the brown pelicans and this appears to be a parental strategy for dealing with unpredictable food supplies. Here's how it works. Within about a 40 hr period, the mother lays 3 eggs, the second egg comes about 24 hrs later and the third one about 40 hr following the first. When the second hatchling appears, the first one is 16% larger. When the third one appears, it is 33% larger! This initial size difference is a competitive asymmetry that gives the first chick a head start and much better odds of survival. The mortality rate is greater for the second and third hatched birds, they feed less and grow more slowly. In the photos below, notice the one that appears smaller than the other two. In the first photo, you can barely see the smaller bird shadowed by its larger siblings.

Brown pelicans are atricial birds, meaning the hatchlings are dependent on parents for long durations. During the first 10-12 weeks, both parents care for the babies that require nourishment and thermoregulation from them. It is during the first month that nestlings experience the highest mortality rate. Success rate of initial clutches is about 50%. Mortality rate in the nest depends on several things including the parents' success at foraging, tick infestion which can lead to nest abandonment, human encrouchment (primarily ground nests) and predators. Feeding the babies requires about 1 lb of fish per day for each nestling. Feeding is a fierce competition for the siblings as seen here.

The nestlings grow in size, and feathers begin to replace the downy white. As wings grow, nestlings exercise them by flapping them vigorously before the bird can even get itself out of the nest. Space becomes an issue as the larger siblings demand more of it, while the smaller birds hang on to whatever is leftover. The pelican must also keep its pouch flexible and does so by stretching it, as seen in the third and fourth photos below. This highly vascularized pouch is the pelican's life blood for many reasons; heat dissipation through fluttering, capturing fish, and as a breeding display.

Brown pelicans are colonial nesters, as few as 10 pairs to as many as 1500 have been observed within a rookery. Typically, there is about a 4-ft distance between nests; but from what I can see, egret nests fill in some of that empty space between, leaving very little room for the large gular-pouched pelicans. Group activity is quite robust as parents tend to their babies while many juveniles and adults hang around seemingly not attending nests. I see many pelicans in juvenile plumage among the adults and nestlings. Brown pelicans do not reach full adult plumage until about 3 yrs and typically do not begin breeding until age 3-5 yrs. But, juvenile pelicans have been known to breed (although not as successfully as their older counterparts) and I have seen juvenile pelicans flying with nesting sticks. What I observe at the rookery seems to be a combination of non-breeding and breeding juveniles mixed with the adult breeders and their young. As a result of the dense population of birds, there is plenty of interaction going on as can be seen here.

Once fledged, the pelican's mortality rate is about 70-75% during the first year, but then declines to about 15% after that. Last year in late May, I watched several young fledglings in the water and flying small distances around the nest islands. Here are a few photos of some of these birds as they learn to care for themselves.

During this trip to the rookery, I noticed several juvenile pelicans flying about. There were lots of flying adults too, some bringing nest sticks back to the nest. I also noticed that the adults no longer had the bright yellow tuft of feathers on their crowns, which are noticeable during the courtship period. Here are a few pelicans lovely in flight.

And finally, knowing that the young nestlings have a low chance of reaching full adulthood (adults, by the way, can live as long as 20 yrs), here are a couple photos to compare. The soon-to-fledge bird in the first photo has less than a 50% chance of getting through the next year. With good genes and luck, this bird will come back to this rookery next year in its juvenile plumage and will then likely grow up to be a parent one day, such as the adult in the second photo.

I can't put all this information into this blog without giving credit where credit it due. Sources of information are the following:

Blus, LJ, & Keahey, JA. Variation in reproductivity with age in the brown pelican. The Auk, 95, 1978.
National Audobon Society's The Sibling Guide to Bird Life & Behavior, 2001.
Saches, EB, & Jodice, PGR. Behavior of parent and nestling brown pelicans during early brood rearing. Waterbirds, 32, 2009.
Schreiber, RW. Nesting chronology of the eastern brown pelican. The Auk, 97, 1980.
Schreiber, RW. Growth and development of nestling brown pelicans. Bird Banding, 47, 1976.
Shields, MA. Establishment and persistence of mass hierarchies in broods of the brown pelican. Wilson Bull, 112, 2000.