Hawk and Cardinal
I love it when the drama of nature unfolds in front of me. Over the last two decades as a naturalist and wildlife photographer I have been privileged to witness all sorts of “national geographic-like” moments and they all still thrill me. Some may remember the story I wrote after photographing a pair of loons that attacked and ultimately killed a Western Grebe. That is an event I will never forget. Well, recently while photographing some birds at a bird feeder, I witnessed another exciting moment in nature. I had been working on photographing Northern Cardinals, a bird which takes an extreme amount of time, patients and a truck load of luck. I usually work on cardinals during winter because their temperament mellows which permits several pairs of cardinals to co-exist without relentless fighting. From deep within the forest a small sharp eyed predator burst on the feeding station sending House Finches, Blue Jays, Dark-eyed Juncos and Cardinals fleeing in all directions. A first year Sharp-shinned Hawk locked onto a male cardinal that was feeding on the ground. While all the other birds escaped to safety this male cardinal was trapped at the base of a large High Bush Cranberry shrub. Studies show that male cardinals are disproportionately taken by hawks and other predators when compared to other birds. It would seem that their bright red feathers make them an easy target. In other words, what is good for attracting a mate is also good for attracting predators. A classic double edge sword scenario. It should seem obvious why the female cardinals are a dull brown color. Anyway, here was this poor male cardinal nervously calling and hopping from branch to branch just 4 feet below the perched Sharp-shinned Hawk. The sharpie’s head was swiveling back and forth watching every move of the cardinal. I could almost see the thought pattern going through the sharpies head. He was calculating at what point should he dive down and make a grab for the cardinal. Meanwhile several thoughts are going through my head. My impulse was to step up and scare away the hawk since I really love these cardinals. But I also love the hawks. I spend dozens of hours waiting for opportunities to photograph these red beauties and if this hawk takes one of my prized males it will mean I will have one less cardinal to photographic in the future. However, on the other hand, I am a professional wildlife photographer and I am sworn to not to interfere with an animal’s natural life cycle and you can’t get more natural than a hawk trying to catch something to eat. So there I stood, concealed in my camouflage watching as the hawk made several attempts to catch the cardinal. The hawk would jump off the branch with its wings folded and drop down to make its way through the thick tangle of branches. The Cardinal would give a loud chip call and jump/fly to the opposite side of the shrub. The hawk would swing around a couple times trying again and again before returning to the top of the shrub where it would sit again eyeing the cardinal and considering its options. This cat and mouse game went on for 5 to 6 minutes, all the time I was cheering for the cardinal yet not wanting to deprive the hawk of something to eat. During these cold winter days a small hawk like this needs to feed at least once a day if it is going to survive. Suddenly and without warning the cardinal summed up enough courage to make a break for it. He bolted at full speed to a larger shrub about 30 feet away. Of course the hawk was in hot pursuit. The sharpie made one last desperate attempt to grab the cardinal in flight but missed, which allowed the cardinal to slip into the thick tangle unharmed. The hawk quickly banked and came to land on a branch of a near-by tree. It seemed the cardinal’s risky move paid off. The hawk sat for a few minutes catching it breath before flying off back into the woods in search of another meal. The male cardinal sat at the bottom of the larger shrub for the next 15 minutes—no doubt counting his blessings. Slowly all the other resident birds emerged from their hiding places and resumed feeding at the feeders. And just like that the drama of nature was over. Now you know one of the reasons I love my job so much. Until next time…
Alaska
I’ve just returned from a wonderful Alaskan adventure complete with bone breaking cold temperatures, snow, erupting volcanoes, avalanches and oceans that never freeze. I have said it before and I will say it again, Alaska is the real deal when it comes to wildlife and wild places. No where else can you find such abundance of birds, land and sea mammals. Winter may seem like a crazy time to visit our largest state but I think it is a magical time. The snow covered mountains and winter landscapes make it a great time to be in the land of the mid-night sun-even if the days are incredibly short. I spend most of my time along the coast of the Kenai peninsula. This is a stretch of land the juts southwest out of Anchorage and is surrounded by the Kachemak Bay. Driving through the mountains which dominant the landscape I saw more moose in 10 days than I do in several years of my normal travels. The streams flow with a slushy green water the consistency of a slurpy. At first glance the water looks uninhabitable but swimming amongst the flowing ice are Common and Barrow’s Goldeneye. These stunning black and white ducks dive beneath the rushing ice to retrieve aquatic insects and crustations off the bottom of the river. Along the banks of the rivers lives a small gray bird that looks somewhat like an American Robin or Gray Catbird. The Dipper is another amazing cold tolerant bird. With much zest and gusto it dives head first into fast moving streams that would sweep you or me away to our deaths in seconds and retrieves tiny aquatic insects which is brings back up to the edge of the water to eat. After eating it simply turns and dives back into the water for another fishing trip. What an amazing tiny bird. One of my all time favorite mammals is the Sea Otter. Just about anywhere along the coast you can see these playful critters. At one time I had stopped to photograph a huge flock so Rock Sandpipers when I noticed about 300 otters swimming and loafing in the water and floating ice burgs. I have seen larger groups of otters in Southern California but never this large. I watched as some would roll around on their backs enjoying the sunshine and feeding on clams and other shellfish while others were play fighting. What a delight. You may have seen in the news a couple weeks ago the irruption of Mount Augustine. This was my first experience with volcanoes and I can tell you I kept my eye on the smoking plume. Thankfully it didn’t erupt during my stay but just seeing the volcano just 75 miles away was exciting. The weather alternated between days of snow and days of sunshine. I don’t believe it got much above 30 degrees during the day and the nights were in the single digits until the last two days when the temps dropped like a rock. One day while photographing Boreal Chickadees, similar to our Black-capped Chickadees, the temps never got above 20 degrees below zero. Coming from Minnesota I was completely prepared for such extreme conditions but that kind of weather can really make you feel alive. But the main reason I went to Alaska was to photograph Bald Eagles. Homer Alaska is the winter home to several hundred of these magnificent birds. I spent many days photographing the eagles fishing from the ocean, flying and banking with snow covered mountains in the background and resting on the rocky beaches. I took thousands of images of these birds documenting all their behaviors and natural history. Even after a week of photographing I was still excited to get up each morning before day break and get out to photograph these birds. Most of these images will go towards a new book I am writing to celebrate our national symbol. I am never disappointed whenever I go to Alaska because as I said before and will say again. Alaska is the real deal. Until next time…
Short-eared Owls
The end of winter can sometimes bring unusual bird species to the northland. One example of this late season addition to our bird list is the recent reports of Short-eared Owls (Asio fammeus). These medium sized owls are one of my favorite owl species. They stand about 15 inches tall compared to 22 inches tall of the more familiar Great Horned Owl. Once found all across the United States their range has shrunk to a handful of western and some central states. From western Dakota’s, south to Missouri and west to the Pacific coast is their current range. During winter they can wonder as far east as New England and sometimes show up in the southern states. The name “Short-eared” comes from the short feather tufts located on the bird’s head. The Great Horned Owl has large feather tufts that are very visible. The tufts of the Short-eared are barely visible and when you do see them the tufts are very short and positioned close together on top of the head. They have the ability to fold the tufts down making them invisible. Short-ears have long wings—long narrow wings with rounded tips. These long wings (just over three feet long) give these owls an easy floating-like flight which is easily recognizable from a distance. Some describe their flight as butterfly-like but I am not so sure I see that when I watch these owls fly. One of the reasons they are one of my favorite owls is because they can be active during the daylight hours when I can see and photograph them. Unlike other owl species, Short-ears sometimes become active an hour or two just before sunset. Sometimes on cloudy windless days during winter they can be seen hunting over fields at midday. Just the fact that it is an owl that can be observed during the day makes this bird more interesting. Most owls hunt from a perched position which is to say, they will sit on a perch and scan the area looking and listening for their prey. Short-ears are much more like a hawk. In fact, they look and act very similar to the Northern Harrier. The Harrier, formerly called “Marsh Hawk”, hunt by flying low over open fields and marshes following the contour of the land scanning the ground for small mammals, birds and reptiles. When they spy something the Harrier quickly turns or drops down in a sneak attack. Short-eared Owls do the exact same thing. The hunting styles and habitat are so similar between these two I would even go as far as saying if you are seeing Harrier’s hunting over a field you have also found the preferred habitat of the Short-eared Owl. Another aspect of the Short-eared Owl that I really like is they are often found in small groups during winter. I often seen 4 to 10 owls hunting over a single grassy field. Late in winter is also the time when the Short-ears become vocal. A group of owls can raise a ruckus with a series of barks. I remember the first time I heard it I though it sounded like a tiny muffled dog barking. With the flood gates of spring about to burst, we can look forward many new and fascinating visitors. I for one can’t wait. Until next time…
Eastern Mole
There are many ways to cope with the cold and snow of another northland winter. Flying south to warmer weather is a popular way for some birds.
Bird Eggs Part 2, The Clutch
Maintaining our spring theme, this week we will continue our look at bird nests, eggs and incubation (see the last Nature Smart column for part one of this series). This time we are going to look at clutches. No, not the thing that helps your car’s transmission change gears. A clutch is defined as the number of eggs produced or incubated at one time by a bird. In general, some species of birds will lay only one egg such as the California Condor, while many birds of prey such as the Bald Eagle will usually lay two eggs. Many song birds such as cardinals and jays will have 4 to 6 eggs while some large birds such as ducks and turkeys will lay as many as 15. The species that get the award for laying the most eggs in one season is the Brown-headed Cowbird. The adult female will produce between 30 and 40 eggs before the season is through. What is even more interesting is, she doesn’t build her own nest to deposit all of these eggs, rather she searches out other bird’s nests and lays an egg in the “host” bird’s nest. Many factors dictate the number of eggs a bird will lay. It’s a combination of factors that determine the number of eggs an individual bird will lay. How long a species lives is one determination. The shorter the birds life, such as a goldfinch or chickadee which on average live about 5 years, the more eggs the female will lay. In addition these birds will often have two or even three clutches of eggs per season. Eastern Bluebirds often have two and some even have three clutches per season. The longer a species lives such as the California Condor which lives to 70 or 80 years lays only one egg every other year. The Common Loon almost always lays two eggs. These birds can live to about 30 years. Food is another clutch size factor. For instance, birds that eat and feed its chicks easily obtained food such as insects will lay more eggs then a bird that specialized in food that it requires skilled hunting. Hawks and owls are good examples of this. A hawk or owl may only catch one mouse or other prey item for every 5 or 6 attempts. The harder it is to catch the food the fewer the chicks. Birds that nest closer to the poles (higher latitudes) have larger clutch sizes due to the high concentrations of insects. If you have ever been to the arctic or even northern Canada or Alaska in summer you know what I mean. Clutch sizes also increase with the type of nest. Cavity nesters such as woodpeckers have increased clutch sizes as compared to open nesters. This speaks to the fact that nest cavities are safer places to incubate and the mother can “invest” all of the seasons’ eggs at one time. Open nesting birds often nest several times a season just in case a predator gets their eggs. Most birds will replace their clutch if it is destroyed by a predator or severe weather. However many single-brood species will not re-lay if their clutch of eggs is lost. In this instance if the clutch is lost early in the nesting season they may be able to replace the eggs providing the female’s hormonal system to recycle into laying mode isn’t shut off for the season. Birds such as Common Loons will not relay eggs if the first clutch is lost while other birds such as the Northern Cardinal will automatically start a new clutch of eggs. Some birds will respond to the removal of an egg. Birds classified as determinate layers will not lay another egg if one is removed whereas indeterminate layers will lay a replacement egg in the absence of one. Younger females tend to lay fewer eggs than older females. Why this is remains a mystery to ornithologists. One idea is, younger birds nest later in the season when clutch sizes tend to decline even in older females. The second clutch of the season (later in the season) is usually smaller then the first based on a strategic adjustment by the laying female to the prospects of finding enough food to feed the growing chicks later in season when fewer food resources are available. As the nesting season progresses we will look at more aspects of this interesting part of a bird’s life. Until next time…
Turkeys
It’s that time of year when the entire country turns it attention to a large and interesting bird—the American Turkey.
Bird Eggs
One of the most remarkable things in nature is the bird egg. So, this week we will continue our series on bird nest and eggs. There are over 9,000 species of birds in the world and all of them lay eggs. By contrast not all mammals, of which there are over 4,000 species, reproduce by live birth. In fact there are two kinds of mammal which reproduce with eggs. These are the spiny anteaters and the platypus, both found in Australia. Talk about your strange animals. Unlike mammals, in which an embryo grows inside the body and is constantly “hooked up” to the mother to obtain its nourishment and other needs, eggs are complete independent from its parents. More importantly an egg needs to be filled with all the protein, carbohydrates, fats, and water that the developing hatchling will need for the duration of the incubation. Just on the surface of it (pun intended) an egg shell is an amazing structure. To start with the shell is the developing embryos first line of defense. So the shell has to be thick enough to be structurally strong enough to not break every time the mother sits on them, but is also must be thin enough to all gases such as oxygen and nitrogen to move free back and forth and at the same time not entomb the chick within when it comes time to emerge from the egg. To prove just how important gas exchange through a bird’s egg is, researchers demonstrated that applying just one-half of a drop of oil per day to a Mallard Duck egg kills the embryo after just a couple days. Even one-tenth that amount of oil killed up to 90 percent of the embryos in another study. Adult nesting birds exposed to even low levels of pesticides or oil in water may bring home enough toxic substance on their belly feathers to kill their eggs. Give that some thought the next time you are applying chemical weed killers to your lawn where your friendly robin likes to run around and feed or when you wash oil down the storm drain into your local pond or lake. The largest eggs of any living bird are those of the Ostrich. They measure approximately 7 by 5 inches and weight nearly 3 pounds. The eggs of some extinct birds such as the elephantbirds of Madagascar measured 15 by 10 inches and weighed as much as 27 pounds or approximately the same as 150 average chicken eggs. The smallest of all bird eggs are laid by the hummingbirds. No big surprise there. Two West Indian species of hummingbird lay the smallest eggs measuring .4 to .5 inches and weigh less than .04 ounces. 75 of these tiny eggs would fit inside one chicken egg. Now that is small! In general the larger the bird the larger the eggs they produce. However in proportion of their body size it doesn’t match up. For example, an Ostrich egg is only 1.7 percent of the bird’s weight, whereas a House Wren’s egg is 13. percent of the weight of the mother that lays it. And there is more interesting aspects of egg size. The females of many species lay smaller eggs in their first nesting season of life then they do later in life. In addition birds that lay a large number of eggs such as Wood Ducks and Mallards tend to lay smaller eggs. In addition the eggs of birds in which their newly hatched chicks leave the nest within hours of hatching (precocial) tend to be larger than similar sized birds whose chicks stay in the nest for many days (altricial) after hatching. Presumably it’s because the larger eggs allow for more development within the egg before hatching instead of doing the final development after hatching. Maybe next time I will take a look at egg shapes. Until next time…
Brush Piles
I recently read a wonderful article by fellow outdoor writer Val Cunningham. With great interest I read her comments about leaving your
Incubation
In the past three columns we have look at and explored many aspects of bird nests and bird eggs. Now in part four I want to look at the next logical topic–incubation. All birds lay external eggs that need to be kept warm throughout their development. This process is called incubation. It may not be an easy process but it is a process that has stood the test of time and seems to work well for the avian world. One interesting aspect of incubation is why at least one or two species of bird have not evolved to give birth to live young. As I mentioned last time, there are a couple mammal species which lay and incubate external eggs, so it reasonable to think that at least one species of bird may give birth to live young. Snakes and other reptiles, which reproduce mainly with external eggs, have many species that give birth to live young. So why not birds? Apparently the advantages of laying eggs have out-weighed the advantages of reproducing with live young. For one thing, with eggs, both parents (or at least in some species) can help incubate or at least keep the eggs warm, thus reducing the burden of incubation. In addition reproducing with eggs would allow the parents to abandon their eggs in the face of deadly danger such as floods, fire, or predators. This would allow the parents to survive and reproduce another brood in another location at a later date. The temperature needed for the development of the embryo within the egg varies across the species. In general, the temperature for incubation in most birds runs between 95 and 100 degrees F. Since air temperatures rarely remain a constant at these levels in the northern states addition heat needs to be provided by the incubating adult. There are some birds such as the Wilson’s Plover which nests near the Gulf of Mexico or the Black-necked Stilts in the Salton Sea of Southern California actually need to cool their eggs during the day but that is another story. Incubating eggs seems like a simple enough process. You just sit on the eggs to keep them warm. Right? Wrong. I think we all know the fabulous insulating properties of feathers–down feathers in particular. Down feathers are the small fluffy inner feathers of a bird that you usually cannot see. If you have ever seen a bird during a snow storm you may have noticed that the snow flakes pile up on the bird without melting. This is another testament to the insulating values of feathers. No body heat is lost through the feathers. So will just sitting on the eggs be enough to transfer enough body heat from the parent to the eggs? NO! A few days before the female (and in some species the male) begins incubating her clutch of eggs her body undergoes a great transformation. The small down feathers on the breast and belly begin to fall out. In most species of duck and goose, the mother pulls or plucks out the down feathers in this region creating an incubation patch (also called a brood patch). In addition to the loss of down feathers the skin becomes swollen through the retention of water in the tissues and more importantly the expansion of the blood vessels that feed blood to the skin. The brood patch takes up much of the area of the belly and breast but is actually concealed by the contour feathers which cover the bird. In other words, the larger, often colored feathers that cover a bird’s body hide the bare skin beneath where the down feathers once were. So the inner layer of a birds two layers of feathers has been removed to expose the brood patch. To incubate a bird spreads apart the contour feathers to expose its brood patch beneath. This allows direct contact to the eggs with the mother’s body thus allowing direct transfer of body heat. Most birds have a body core temperature somewhere between 98-105 F which allows the mother to rapidly warm her eggs and maintain the warm temperatures over a long period of time. How long a bird must sit on there eggs will be the subject next time. Until then…
Part 5 Baby Birds
Over the past four Nature Smart columns we have followed the progression of birds building nests, how mother birds lay eggs, the intricacies of incubation and so much more. So it only makes sense that this time we finalize this series by examining baby birds. Nearing the end of incubation period, while still in the egg, the chick develops an egg tooth which is a short pointed structure on the tip of the upper beak pointing upwards. This “tooth” is used to break its way out of the shell. Or more accurately put, scrap its way out of the shell. The chick within the egg is generally in the fetal position with its head towards the belly. With specialized muscles the chick straightens out enough to rub the egg tooth against the inner wall of the shell. Also, at this point the egg has been weakened by the absorption of calcium by the developing chick. The constant rubbing of the egg tooth against the inner shell produces a small hole in the shell which is called pipping or the egg is pipped. Then the chick scrapes another hole in the egg, usually on the blunt end of the egg. Once enough holes are created the chick pushes out of the shell. This process take a lot of strength and once the chick has emerged from the shell it often lays very still for a long time while it gathers up its strength. The time between pipping and hatching can vary greatly from species to species. Most small birds take up to 6 hours to complete the process while some very large birds make take up to 5 days. Once the chick has hatched the egg tooth is absorbed back into the beak or the tooth falls off. Baby birds are classified in one of two ways when they are hatched. The first is called altricial. These baby birds are what you think of when you envision a young bird. They are born with their eyes closed, have very few if any feathers, are unable to move around very well, have no ability to regulate their own body temperature and are completely dependent upon their parents for everything from warmth to food. An example of this kind of bird would be most songbirds such as robins, blue jays and cardinals. Altricial birds look like they have huge jelly bellies with a tiny head and two bulging eyes that are sealed shut. About the only thing these tiny helpless birds can do is hold their heads straight up and open their mouths (gape). This may seem very simple but it is also very important. The inside lining of the baby birds mouth is often a bright red or orange and acts to stimulate the parents to feed the babies. These birds have no feathers to conserve warmth and in addition they have no ability to regulate their body temperature. The parents need to brood (see the last column) to keep them warm. Baby birds grow so fast you can almost see it before your very eyes. Over the next 5 or 6 days most birds will develop feathers, their eyes will open and they will be able to maintain their body temperature on their own. They can move around the nest freely and they start to flap their wings. In another week to ten days the young will be ready to leave the nest. The second type of new born bird is called precocial. These birds have their eyes fully open and functional, are able to walk, run, or swim depending upon the species, feed themselves, fully feathered and have no problems regulating their body heat. An example of a precocial bird is ducks, geese and most shorebirds. So there you have it. Everything you ever wanted to know about bird nests, eggs, incubation and so much more. Until next time…