Snow Goose Migration
There are many marvelous places or natural events in the world that can dazzle your eyes and entertain your mind. I am fortunate enough to travel and photograph some of these amazing events and places. Some of these marvels of nature are well known such as the migration of wildebeest on the plains of east Africa. One and a half million animals move across the African plain covering nearly 2,000 miles in search of fresh green grass each year. The gathering of the Andean Flamingos in South America is another great example of a special natural event. Tens of thousands of long legged pink birds gather in huge flocks in shallow lakes to feed. It’s certainly a pink spectacle unmatched in the world. Closer to home the Grand Canyon is a good example of a natural place. Spanning 277 miles long and up to 18 miles wide the Grand Canyon is unmatched in its grandeur and splendor. All you need to do is stand at the rim and gaze upon the canyon to know what I mean. The problem with many of these amazing natural events and places is they are often in far away places and only accessible by those with enough time and money. However there is a natural marvel that rivals the great events of Africa and South America much closer to home. It is the annual migration of the Sandhill Crane and Snow Goose in south central Nebraska. Yep, that’s right—Nebraska. I have just returned from leading a bird watching / photography trip for four days of eye popping, jaw dropping natural spender. And the best part is, I didn’t have to take malaria pills, update my health insurance or break out my passport. I have traveled to Nebraska each spring for nearly 20 years and I still get excited at witnessing this ancient event unfold before my eyes. For the past 20,000 years, nearly a half a million Sandhill Cranes and millions of Snow Geese funnel down to an 80 mile stretch of the Platte River for the first leg of their migration to nesting grounds. After spending the winter scattered in Texas, New Mexico, Arizona and Mexico, the cranes and geese start to move north in mid February. Over a 6 to 8 week period of time, millions and millions of birds bottle neck down to this special place in Nebraska where they will feed and put on enough body fat to fuel their journey to the breeding grounds in Canada and Alaska. Each evening my group of bird watchers and photographers would end up near the Platte River to watch the cranes return from feeding in the surrounding fields. Both the cranes and the geese return to the sandbars in the river just after sunset, using the water as a mote of protection from predators. We would watch from the banks of the river as thousands of cranes and geese would fill the sky, swirl around and around before finally settling down on the safety of the sandbars in the river. The orange sky in the west was a perfect backdrop to this spectacular natural event rendering the birds moving black silhouettes in the fiery sky. The accompanying sounds of this huge mass of birds all calling together added greatly to the magic of the moment. I can say in all confidence that the annual migration of the Sandhill Crane and Snow Goose is North America’s most amazing natural spectacle and is in the top 10 natural events in the world, and I am not the only one who feels this way. I recently saw a television show featuring Jane Goodall, famed primatologist and world traveler, who said she felt the migration of the Sandhill Crane and Snow Goose in Nebraska was one of the most remarkable natural spectacles on the earth and that it shouldn’t be missed. She comes to Nebraska each spring to see it for herself. I couldn’t agree more and that’s why I come back year after year. Until next time…
Rarities
Chasing down and photographing rare birds has never been my thing but lately I seem to have run into some of the most uncommon or rare birds in the entire country. During the first week of March I was leading a trip to Nebraska for the annual migration of Sandhill Cranes and Snow Geese. This is a regular trip for me and I expect to see some amazing things such as tens of thousands of cranes filling the evening sky. I might even expect to see, if I am very lucky, a Whooping Crane mixed in the thousands of Sandhill Cranes. Whooping Cranes are very uncommon birds with populations numbering only in the hundreds. However within 30 minutes of arriving in south central Nebraska, I pulled up to a large flock of cranes feeding in a corn field near the road. Immediately I noticed an unusual crane standing on the edge of the flock. Of course the first thing I did was grab my camera and ripped off a couple shots to make sure I had a record of the bird before it took off. Having never seen this kind of crane before I knew it was something special. A few seconds later the crane took off with the rest of the flock. A quick check of the first field guide gave me no clue. The bird was not in the guide. Fortunately a friend had another field guide which did include the identity. We had found a Common Crane which is a kind of crane found in Eurasia and not found in North America. Our group broke into cheers at the fact that we found such a rare bird. A few phone calls later and we found out that this bird is probably the only one of its kind in the country in the wild. Fast forward three week and I am in south Texas Rio Grand Valley where I am writing this column. This time I am working on photographing birds and animals for several new field guides for the state of Texas. While talking to some friends at a local gathering one evening I was told of a rare bird. For the past couple of weeks a White-throated Robin has been seen feeding in a mulberry tree in a town near by. So the next day I head over to see what I can find. I am traveling with 3 other professional wildlife photographers and it was an interest to all of us. Within 10 minutes of arriving in the area we locate the bird feeding on ripening mulberries but the bird stays deep within the inter part of the tree and never leaves the dark shadows. We set up our cameras and begin the waiting process. An hour passes and nothing. We can see parts of the bird, a wing here and a tail there between the branches and leaves but we can’t get a shot of the entire bird. The bird is actively feeding on the berries and doesn’t even notice us. Then all of a sudden, a bird that looks like a robin with a bright white throat, hops out into the open on a branch and the cameras start clicking in rapid fire mode. The bird remains out in the open for another few seconds before flying back into the shadowy interior part of the tree. We are thrilled. High fives all around. The white-throated Robin (Turdus assimilis) normally occurs in the mountains of Mexico. The first one ever recorded in the US was in Laguna Vista, Cameron Co. Texas on Feb 18, 1990. This bird was coming to a feeder with other birds. The second record of a White-throated Robin in the US came in February 1998, also in Texas. Then on March 18, 2008, Allen Williams, a resident of Pharr, Texas found a White-throated Robin feeding on mulberries in his rather large backyard. About a week later I was there to see and photograph this very rare bird in the US. I guess you don’t need to chase down rare birds in order to see these rarities. Sometimes being in the right place at the right time is just as good. Until next time…
The Rituals of Spring
This time of year is filled with ancient rituals. Rituals that ensure the survival of the natural world. Each spring, as it has for ten’s of thousands of years, and in some species even millions of years, birds and animals strut, sing, show off, chase, cajole, or whatever it takes to find a mate with the sole objective of reproducing. The huge diversity of bird and animal species has lead to a wide variety of ways in which the males prove to the females that they are worthy fathers and that the females are worthy mothers. All of these spring rituals are all triggered by the amount of available daylight and signals the start of the breeding season. As the world tilts on its axis and the sun slowly get higher in the sky we gain more daylight. With each passing day in spring we gain more daylight. In fact we have gained over 5 hours of daylight since the winter solstice, which is the shortest daylight of the year, back in December. The amount of daylight is called the photo-period. The photo-period is what indicates or triggers the mating response in birds and animals. In the case of the mammals they perceive the daylight through their eyes and is passed onto the brain. We humans are the same way. We feel different at this time of year because of the amount of daylight we perceive with our eyes. Birds on the other hand perceive daylight directly into their brains through their skulls. A direct signal to the brain from the outside world if you will. Once the brain has been informed of the amount of daylight, it triggers hormones to be released that flow though the animals or birds body that awakens the reproductive organs which lay dormant for most of the year. Unlike humans, most animals and birds can only mate during a brief period of time each spring. That is not true for all birds and animals but it is true for most. Once the reproductive organs are up and running, the mating rituals begin. In the bird world, the males are the ones all dressed up to impress. The males of many bird species have brightly colored feathers that are designed to do one thing—communicate to the female that he is good and strong with a abundant food supply within his territory. In addition the males augment their brightly colored feathers with songs. Bird songs are as ancient as their bird species that are singing the songs. Many songbirds have been around for hundreds of thousands of years. Songbirds are a specialized group of birds that have wonderful complex songs that usually only the male sings. There are a few species that break the rules and both the male and female sing, such as the Northern Cardinal. But in general it’s usually just the male that sings. Birds that are not songbirds such as the Wild Turkey don’t sing a song at all. They rely on visual display to show that the male is a strong healthy bird and worth mating with. He will fan out his tail feathers, droop his wings so the wingtips are dragging on the ground and puff up his iridescent body feathers to impress the gals. He even has large patches of exposed skin around his head that change color from red to blue and white. Male turkeys give a hissing and popping noise over and over as he tries to maneuver himself in front of the females in his group so they can get a good look at his magnificence. Only when the females are ready to nest will they pay him any attention and allow mating. The actual mating is brief but the courtship goes on for weeks. While he waits for her readiness, he will strut around and around so she won’t forget he is ready. Strutting male turkeys is a ritual that I look forward to seeing and photographing each spring. In my mind it’s an ancient ritual that indicates spring. I can spend hours watching the males do their thing. I get a sense of security and permanence and that all is right in nature when I see this ancient dance. For you the rituals of spring may be the singing of a male robin or the mate chasing of the Eastern Gray Squirrel in your backyard. Cottontail rabbits will also chase each other across your lawn and jump high into the air for their mating ritual. No mater what the spring ritual, remember these are important aspects to a healthy environment and it’s a ritual that ensures these birds and animals will be around for many more generations, but only when the sun climbs high into the spring sky. Until next time…
Woodcock
Dust billows up from behind my truck as I drive down the dirt road to my favorite location to see and photograph a strange little bird known as the timber doodle. Stopping on the side of the road, I step from my truck into a picture perfect late evening. The sun has just set but the western sky still glows bright orange and the sky is crystal clear. I love evenings like this. Quickly I set up my tripod, camera, and most import, my flash. I grab my flashlight and walk towards a wet field with small trees on the edge of a large stand of woods. As I walk, I flash back nearly 30 years. I was a young naturalist, wide eyed and eager to see all the natural world had to offer. I am walking into the same field, this time with the best naturalist I have even known at my side. She is showing me the display flight of the timber doodle. What the heck is a timber doodle I ask her? She responds with the bird’s real name, American Woodcock. Oh, I said, still not knowing what the heck she is talking about. Shortly after sunset, we stand in the field and wait quietly. A near by pond filled with Western Chorus Frogs is filling the night with their loud mating call. Then a loud noise breaks from the grass in front of us. It sounds like an electric buzzer. It’s the call of the American Woodcock. Every few seconds it gives another call—“peent”. Then suddenly it flies from the grass into the fading evening light. It flies up to a height of a couple hundred feet then starts to fly in a tight circle directly over our heads. I remember standing there, looking up and watching the display with my mouth open in utter wonderment. I can hear a twittering and whistling noises coming from the woodcock above my head. It flies around and around several times before suddenly it drops from the sky like a rock, landing back where it left the ground and then it starts to call again—“peent”. That was my first experience with the mating display flight of the American Woodcock. It is something I will never forget. Flash forward to present time, and I am walking with my camera into the field in the fading evening light. I have the same experience of flashing back and remembering my first experience each and every time I come to see the woodcock display flight. The American Woodcock (Scolopax minor) is a plump, short legged shorebird that isn’t found at the shore. It favorite places are damp or wet meadows. It has a large head with an extremely long bill used to probe deep into the wet soils for insects and earthworms. It has huge eyes that are placed on either side of its head giving it the ability to see in front and behind at the same time. The males perform this elaborate evening courtship flight each spring to impress the girls. Presumably the females are nearby on the ground, listening for a male with loud calls a good flight pattern. When she seen a male that is to her liking, she will approach the male on the ground. Together they will fly off a short distance to a location near by and mate. Afterwards the male returns to his dancing field and she will head back into the woods to find a place to nest which is usually at the base of a large tree. Tonight I am here to photograph the male woodcock. I work my way into the field as quietly as possible and I wait. I am enjoying the end of the day and it’s getting very dark. From just 50 feet away I hear the first call of the night. I work my way up closer just as the male takes to the sky to perform his sky dance just as he and many generations before him have done for countless years. His flight is perfect and he comes back down not 25 feet away from me and starts to call. I turn on my flashlight and spot him standing in the grass. Quickly I focus my camera and push the shutter release. The flash from my camera goes off and lights up the small woodland meadow. The male doesn’t even blink an eye, he just goes on calling. I’ve got my shot. Many years have passed since that first night and there have been very few springs where I haven’t come to witness the woodcock display flight. Now I bring my wife and daughter to this place to see the magical sky dance of the woodcock. The field is the same but it is filling in with trees. The Chorus Frogs are still calling from the small pond and the woodcock are still dancing and displaying and I am still hear to see the dance of the timber doodle. Until next time…
Rushing Grebes
My alarm goes off at 4 AM and I am up and out of bed in seconds. Minutes later I am in my truck driving north in the darkness of another beautiful spring morning. The stars are still shinning and the moon is full and setting in the western sky. As I drive north, the eastern sky starts to glow orange and red. I have a feeling of anticipation in my stomach, or was that hunger, I’m not sure. Two and a half hours later we are backing the boat into the lake. My good friend and fellow photographer Buck Huber and I are heading out on a large lake in Central Minnesota to photograph one of the most exciting courtship dances of all the North American birds—Western Grebes (Aechmophorus occidentalis). The Western Grebe is a large long-necked water bird that has a black cap and a two tone neck– black in the back and white in the front. It has a deep red eye and a long narrow yellowish green bill. They range from western Minnesota and the Dakotas as far west as Oregon and California and as far south as Colorado. But I am not here to photograph a bird sitting around in the water. No, I am here for the “rush” and the “dance”. So right about now you are thinking, what the heck is this guy taking about? The Western Grebe is a bird with a highly unusual mating ritual. About a week after the ice leaves the northern lakes, flocks of Western Grebes migrate back to lakes where they have been breeding for hundreds and in some cases thousands of years. They are colonial nesters which mean hundreds of pairs of birds all nest in the same area. In many instances their nests are only 5 to 6 feet apart. Nests are located in cattails and bulrush along lakeshores. Each nest is constructed with the dead aquatic plants from last year. Nests are a flat mat of floating vegetation that holds up to four off-white eggs in a shallow cup. These birds are monogamous and it’s unknown if they mate with the same partner each season. Now here comes the fun part. Western Grebes are well known for their many and spectacular displays. In fact they have so many displays I can’t write about them all so I will limit it to the most obvious. First is the rush. When a male and female are apart for a short period of time, usually one is off fishing, upon returning they will greet each other with several loud calls. As they swim closer together their heads get low to the surface of the water and they ratchet their heads back and for. Suddenly they both spring from the water’s surface and run across the water, with their necks extended straight up and their heads cocked at an angle so their bills are pointing upward. Their wings are head open over their backs and using their extremely large feet, they run across the waters surface, side by side for up to 20 feet before they slow down and dive head first into the water. The rush is over. After the rush, the birds resurface and only now and then, maybe only one in 50 rushes, do they follow up with one more remarkable display—the weed dance. Both birds will dive to the bottom of the lake and pick up some green plants. Resurfacing they swim together and once again rise up out of the water, stretching their necks upwards and as if they are presenting the gifts to one another. They shake and turn their heads back and forth as if to say look at what I brought you. This lasts about 20 seconds and they drop the weeds and swim off together. Wow, now that is a display. I remember as a kid in the 1960’s watching this very scene on a nature program on our black and white TV, and thinking how cool it looked and that some day I would like to see it. And now that I am watching it in person, I’m thinking it’s even better in color. I have traveled to this colony of Western Grebes 4 times over the past 2 weeks and was only really successful at capturing these amazing images on just one of the trips. All total I spent 25 to 30 hours crouched over in the boat hiding in the weeds to get these images, not including drive time, but I think it was well worth it. Until next time…
Nesting Birds
I am always impressed with birds, in particular in how successful they are as a species and their amazing diversity. I think as people we often take the birds for granted and that they are just a “normal” part of nature. Oh sure they are beautiful to look at but do we actually “look” at them? Do we spend any time sitting and watching? Do we consider how different they are or how small and fragile they are? Recently I found myself thinking about these very questions. Just yesterday at sunrise on a early summer morning. The sky was clear and blue, the sun had just come up and the winds were calm. Nothing short of a perfect morning. I was spending a few days at my cabin on a lake with my wife and daughter and had taken some time early in the morning before they got up to photograph a Yellow Warbler nest. I had slowly moved closer and closer to the nest over a 30 minute period of time so the mother Yellow Warbler would become comfortable with me. I used the trees and shrubs between us as a natural barrier to make the tiny warbler feel more safe. Slowly I got within photographic range then settled in for a while so she would get very comfortable with me before I started photographing. I sat and watched as the mother warbler move about the shrubs and trees gathering caterpillars, spiders and other insects to bring back to the nest. She would wait until she had several stuffed in her bill before returning to the nest to feed the young. Interestingly, she never left a 10 foot radius around the nest to gather the food for your newly hatched chicks. I could hear the male Yellow Warbler singing near by but he seemed to stay away most of the time. Occasionally he would show up with a big fat caterpillar and she would eagerly greet him and she would act like a baby bird herself by fluttering her wings and bowing before accept the caterpillar offering from the male. She would immediately return to the nest with the caterpillar and stand over the young in the nest as has if to say, “Look what your father brought you” and feed one of the hungry chicks. Then off she would go to look for more food. After I knew she was comfortable with me be near by and had made many trips to the nest to feed the young I started to photograph. This is an important part of wildlife photography. In order to get natural behaviors and real action shots you need to sit and watch and learn what the bird is doing and also give it time to get comfortable with you being so close before taking any pictures. Once I started taking some pictures the mother warbler didn’t even look up or react a tiny bit to my camera shutter or my flash going off. I had successfully introduced myself to this wonderful creature. Over the next couple hours I photograph the comings and goings of the mother as she feed the incredibly tiny chicks. At this stage of life these birds are no larger than a lima bean. They a sparsely covered with feathers, their eyes are sealed shut and they only have enough energy to lift their heads for a few seconds before collapsing on the floor of the nest in exhaustion. But time and time again the mother flew to the edge of the nest and three tiny heads would lift up and she would deliver her insect meal and the babies would crumble in a heap. About every third or fourth visit the mother would settle down and sit on the chicks to keep them warm. This is a process called brooding. Chicks this small don’t have the ability to regular their own body temperatures very well so the mother still needs to keep them warm. Feeling like I got several nice images, I slowly packed up my stuff and waited for a time when the mother wasn’t watching to creep away from the nest, being careful not to disturb the tiny amazing bird family. Until next time…
Turtles
It’s turtle time of year. The time of year when turtles are seen crossing roads, traversing backyards, and just about anywhere else you might look. The other day I was stopped at a traffic light and looked to my left. A large truck towing an even larger trailer was skidding to a stop in the turn lane. Just in front of the truck was a large snapping turtle crossing the road. When the truck came to a stop the passenger door flew open and a guy got jumped out and trotted up to the snapper, grabbed it and walked the turtle to the side of the road where a small pond was and released it. I thought to myself, turtles could use more friends like these two guys. I have done this very thing hundreds of times over the years. So what are turtles doing when they are crossing roads and wondering in backyards? Well, most likely they are female turtles who are looking for a place to lay their eggs. Turtles spend most of the life in water. In spring and early summer male turtles seek out females for mating. Male turtles in most species tend to be slightly smaller and have extra long front claws that help them hold onto the edge of the females upper shell during mating. Males also have a concave area on their lower shell (plastron) that fits over the domed upper shell (carapace) of the female. Once the male has mounted the female a packet of sperm is passed from the male to the female which will fertilizes the developing eggs. The female has a short window of time where she needs to find a suitable place dig a nest and lay her eggs. Unlike birds, turtles don’t incubate their eggs but rather they leave it to the sun warmed earth to incubate. The female turtle will leave her lake or pond and travel up to a half mile until she finds a place where the soil is soft enough to dig an egg chamber. Sandy soil is often chosen because it’s easy to excavate. Using only her back legs and feet, she begins the digging process by wetting the soils with extra water she has stored in her bladder. One scoop of her hind feet at a time she begins to dig the nest chamber. It’s a slow process that she can’t see because it behind her. If she is disturbed during this time she will abandon and head back for the water. A nest chamber of a Painted Turtle is no deeper than 3 to 6 inches deep, or the depth in which she can reach with her hind feet. In the chamber she will deposit 5-20 pink to white leathery eggs. Once she starts to lay the eggs the female usually isn’t scared off and is completely vulnerable to predators. Once the eggs are deposited in the chamber she takes great care to back-fill the chamber with dirt and tamp it down. She even goes as far as moving debris over the chamber to completely camouflage the location. Once this is done the female usually makes a bee-line back to the safety of the water. Just yesterday I watched a female painted turtle (see photo) dig a chamber and lay 6 eggs in less than 30 minutes. She may have several nests in one season but it’s usually several days or weeks between nesting. Now it’s up to the sun to warm the earth and incubate the eggs. This is the dangerous time. Most studies show that 70-90 percent of all turtle nests are predated by raccoons, skunks, domestic cats, dogs, opossum, fox, coyote and just about any other animal that has a nose good enough to smell the buried eggs. In most species of turtles, the chamber temperature during incubation determines the sex of the offspring. Generally speaking, warmer nests incubated at around 84-87 degrees F, produce mainly females. Cooler nests at 76-77 F, produce mainly males. Nests incubated at 82-84 F produce a mix of males and females. For the painted turtle the length of incubation is 70-80 days, so eggs laid now won’t hatch until September or October. If the weather is good when they hatch, the young will emerge from the chamber this fall and head directly to the lake. However later hatching young turtles will remain underground in their nest until the following spring before heading to the lake which starts the entire process all over again. Until next time…
Hummingbirds
Mid-summer can be a slow time in the wildlife photography business. Most of the nesting birds are done raised their young and have retreated to the forests and fields to feed on insects and live a few weeks of the good life before gearing up for migration. So in mid-summer I find that I turn to hummingbirds for photographic opportunities. Of the nearly 9,000 species of birds in the world, about 320 are a kind of hummingbird. (By the way, that is a lot.) The majority of these hummers are found in the tropical regions of the world. In North America there are 17 species of hummers with most of these found in southeastern Arizona. Sorry to say, we only have one species of hummer in the northland–the Ruby-throated Hummingbirds (Archilochus colubris). The ruby-throat is a tiny bird measuring only 3” long. Females are slightly larger than the males and have longer bills. An individual hummer weights only 2-3 grams; it takes 5 hummingbirds to equal the weight of a single Black-capped Chickadee and we all know how small the chickadee is. Ruby-throated Hummingbirds often appear to be gray in color when viewed in dim or low light but are bright green when seen in direct sunlight. They have specialized feathers that contain individual cells that will absorb sunlight and reflect only the green spectrum of the sunlight back to our eyes, making them appear green. Males have a throat patch of specialized feathers called a gorget. The gorget appears black in color until he turns to face you. When sunlight hits the gorget patch it lights up in a brilliant ruby red color as if someone has flipped a switch to a neon red light. The bright ruby color is also a result of reflected sunlight. The gorget is used to impress females for mating. The bigger and brighter the gorget the more the females are attracted. Hummingbirds received their name from the “humming” noise created by their wings whiz through the air. Hummingbirds flap around 50-60 times per second during normal flight and can reach up to 200 beats per second during courtship flights. (Try doing anything 200 times per second.) They can fly up to 50 mph and usually fly no higher than 300 feet. Hummingbirds can hover, fly up and down, and are also the only birds that can fly backwards. To power all of that wing activity, the hummers have very large hearts that beat at an amazing 1,260 beats per minute compared to our own heart that beats about 70 – 80 beats per minute. Their heart is so large it comprises one quarter of a hummers total body weight. They fuel all of their muscle activity with oxygen. They breathe 250 times per minute compared to our own respiratory effort of 12-18 per minute. To keep these flying machines going, hummingbirds have a metabolism that is 40 times faster than our own. They survive on top line fuel—fast acting sucrose (a kind of sugar) obtained from flower nectar. They consume up to 50 % of their own weight in nectar daily. That would be the same as you or I drinking a bathtub of soda daily. Hummers feed on nectar about every 10 minutes throughout the day but flower nectar is not the only food on their menu. Tiny insects such as gnats and flees make up most of their non-nectar diet and provide them with the protein not found in a sugar water diet. So for me, if it’s mid-summer, than it’s hummer time. Until next time…
Cowbirds
I love how people think of some birds as “good” and other as “bad”. They feel that some birds are actually nice and friendly while others are mean and ill-spirited. They even go as far as thinking that some birds are welcome at their feeders while others are not. Well, I’m not one of those judgmental people. I like all birds. In fact I have never met a bird that I didn’t like. The Brown-headed Cowbird (Molothrus ater) is one of those birds that many people don’t like and I might go as far as to say that some people hate this bird. Again, I don’t understand this kind of thinking because I am truly amazed by this bird. So why do some people hate this bird? Let me explain. The cowbird is a nest parasite. The female doesn’t build her own nest to lay her eggs in. No, instead, she finds the nests of other birds and relies on these “host” families to incubate and raise her young. During the breeding season a female cowbird will mate then slip off to parasitize other nests. More than 220 species of birds are parasitized by cowbirds. Of these about 140 species actually knowingly incubate and raise the young cowbirds. For years naturalist like myself and researchers have wondered why do these birds knowingly raise a young cowbird to the detriment of their own young. Studies indicate that birds such as warblers that raise a cowbird chick have on average 3 of their own while warblers who don’t have a cowbird chick raise 4 of their own so its obvious that the warbler is not benefiting from hosting a cowbird. A recent study which was modeled after a study originally preformed in the 1940’s gives us some insight into this conundrum. It turns out that cowbirds use mafia like tactics to insure they young are raised and it goes something like this. When a female cowbird finds a nest she will deposit one of her own eggs then she removes one of the host birds eggs. By the way, a female cowbird can lay up to 40 eggs in a single season which must be some kind of record because most birds usually can produce less than ten. In the study the researchers took the cowbird egg out of some of the warbler nests while in other nests the cowbird egg was left. In 56 percent of the nests where the cowbird egg was removed, the female cowbird came back and destroyed all of the warbler’s eggs and nest thus sending the message “if you don’t raise my baby, I will take out your entire family”. In the nests where the cowbird egg was left, only 6 percent were depredated. So this leaves the host birds with not much of a choice, either raise a cowbird chick or nothing at all. Now that is what I call a fascinating story. Until next time…
Seasonal Changes
We are coming up on a very confusing time of year for many wild critters. It’s a time when the birds are getting ready to migrate and frogs are preparing to burrow into the earth for the long cold winter. But that’s not the confusing part. The confusing part is when these critters start to do something that they normally do only in spring—they start to give mating calls. Each autumn this strange phenomenon happens. Birds such as the Northern Cardinal and American Robin perch up high in a tree and start to sing their breeding songs as if it were spring. If that’s not enough, several species of frog start to call from the shallow ponds. It’s like a mini-spring breeding season all over again. So why do they do it? Well it all has to do with something called gonadal recrudescence. Hold on, I know what you are thinking, don’t give up on this story just yet. Read on. Each spring birds, mammals, reptiles and amphibians use environmental cues to indicate when it’s time to breed. More specifically they use the amount of daylight (sunshine) available each day, kind of like a luminous calendar. The amount of light in a day is called the photoperiod. In mammals the length of daylight is perceived through its eyes. In birds and amphibians the daylight is perceived or absorbed right through the skull and or body. Either way a photoperiod signal is sent to a gland in the critters brain called the hypothalamus which is connected by a thin stalk to the pituitary gland. The pituitary gland sends out gonadotrophic hormone into the body which acts upon the testes of males and the ovaries of the females putting the bird or amphibian into breeding condition. It’s like turning on a breeding switch. During the breeding season the testes of male birds will grow several hundred times their non-breeding size and weight and become active in preparation of mating. A similar process happens in female birds. The ovary of the female bird swells and starts to produce ovum which is the beginning stages of egg development. After the breeding season the testes and ovaries of these birds regress or shrink and become inactive and the breeding season is over for the year. It’s important that this happens after migration because the extra weight and size during migration would only serve to use up more energy and slow the bird down during migration. However in late summer the photoperiod or the amount of available daylight matches the photoperiod of the spring breeding season and the critters hypothalamus picks up on this signal and is temporarily tricked into thinking its spring. This is where gonadal recrudescence occurs. Recrudescence means to break out anew after a dormant period and that is what happens. The testes of the males and the ovaries of the females temporarily start to swell and become active again. So for a short couple of days or maybe a week the birds and frogs are tricked into thinking it’s breeding season based on the available daylight (photoperiod) and the birds start to sing and the frogs begin to croak. It doesn’t last long before the photoperiod shortens as the days shorten and the hypothalamus is no longer stimulated and the puitary gland stops sending out hormones to the testes and ovary and the bird returns to a non-breeding condition again. So if you hear a bird singing from a tree or a frog calling from your local pond in late summer you can be thankful you are not as controlled by your hormones as the birds and frogs are. Or are you? Until next time…