Tag Archives: sandhill cranes

Flying High

6 Nov

Last night on the way back from town, I observed and drove along with a flock of ~250-300 sandhill cranes returning to the refuge from foraging north of here. (Couldn’t do an accurate flight count and drive at the same time.)

Observing the flight dynamics of this group was really quite interesting. Unlike Canada geese that typically form several dynamic ‘V’ patterns, this flock of cranes did not. Except for the front ‘V’ with a very truncated side ‘arm’ of five individual cranes, the rest of the flock was one long linear flock stretching for a few miles.

Typically with geese the front leading bird of the ‘V’ formation frequently changes, trading places with nearby individuals. This seems logical because energy is then conserved among the leading birds. Not so with this flock. The leading crane never left its position as lead and never ‘coasted’ in flight, aka never altering or ceasing wing-flap flight. I was impressed, but also suspected it was very energy consumptive. Additionally, the five cranes forming the truncated arm behind the leader never changed positions and also never faltered in consistent wing activity.

The cranes following in line behind the leader, on the other hand, often coasted with short periods of folding wings alongside their bodies. Whether this was to rest (energy conservation) or to retain their position in the long line, I cannot be sure. I did notice that some individuals did change positions when some birds slowed or fell slightly out of line. Consequently, the line was truly maintained as one long linear fight pattern! I also wondered how many of these birds were immature cranes who aren’t yet as strong as the older adults, or if they haven’t yet mastered the ‘protocol’ of flying in large flocks. I watched one crane fly under and ahead of five other cranes in front of its former position and fill in a gap in the line. It reminded me of how blackbirds and other flock songbirds change positions while roosting on utility lines, with some hop-scotching to keep a tight and consistent line formation.

I was fascinated by the flock and flying dynamics of these several hundred sandhill cranes! Very different from the geese. Although my original intent was just to monitor where this flock landed, I was treated to an entirely different perspective of flock flying dynamics.

Because questions of daily roosting versus feeding movements and populations of sandhill cranes arose during a meeting between state and federal managers this week, I thought watching where this flock was destined might be interesting. Only a small percentage of the total flock (~24) landed on the small ‘crane ponds’ (small shallow water impoundments just north of the main refuge where cranes often roost). I expected a higher sub-set of this flock to land there. I briefly watched these birds try to locate the members of their family units for roosting overnight, then I drove ahead to monitor the remainder of the flock.

As the larger sub-set of birds approached the center of the refuge where two large impoundments are shallowly flooded for roosting and feeding, the linearity of the flock dissolved as smaller flocks formed and dispersed. Approximately 50% of the flock settled on these impoundments, and the other 50% flew east to roost on the sandbars of the Rio Grande River.

New Mexico state biologists survey populations of waterfowl on the river via aerial surveillance once a month. This refuge conducts feeding surveys every week. We are discussing now whether to incorporate ground roosting surveys for geese and cranes once or twice/month to add to the total data on use of the resources and land in the mid-Rio Grande Valley, especially since most of the cranes now present here are flying north to feed during the day at state-managed refuges (~38 and ~60 miles north of here).

Estimating the light geese roosting population would be easier than that of the cranes because the former typically take flight in one large massive flock. Cranes, on the other hand, usually depart from their overnight roosting places in small family units of 2-4. However, cranes congregate in overnight roosting  flocks at only a few locations on the refuge. Counters posted at each of these locations can easily count the family units and obtain total numbers as they take flight. It might take longer, but it might also be more enjoyable.

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Feeding sandhill cranes at Bosque del Apache NWR

What color are we today?

3 Jan

Male & female Mallard ducks in winter plumage

Since immersing myself in the observation and science of birds, I’ve learned that they might outdo humans in levels of complexity. I must admit, however, that birds are a tad easier to understand simply because they lack the capability to think in abstracts. Unless you watch Loony Tunes’ Wiley and Roadrunner cartoons.

Regardless, one of the many aspects about birds that incites my curiosity is the vast and complex diversity of coloration. This is also a source of understandable but frustrating confusion for many people when attempting to identify birds. Most guidebooks may describe and illustrate only one or two of the color variations that a bird species might show. On the other hand, many bird species may exhibit variations of colored plumage throughout the year depending on the season, their age, and their sex. This often befuddles attempts to identify a bird people see, especially if the bird in question might be a vagrant to their local area, in between-seasonal plumage, or an intermediate between two subspecies.

Understanding the basis for individual variations in a bird species can enhance observers’ identification skills. Consequently, I will address some of the topics that directly and indirectly contribute to bird plumage variations in a series of posts. Additionally, because of my interests in evolutionary biology and genetics, side topics touching on some of the fun things (in my opinion) will also appear. I do this simply because of the ‘why’ and ‘how’ questions that often arise in conversation with other people, which indicate to me that even non-scientists are curious.

Birds of the same feather don’t always flock together

The most direct difference between males and females (sexual dimorphism) is sexual organs. However, examples of secondary differences, those most obvious to our eyes, include body size, behavior, ornamentation and coloration.

For many animals, it’s all about appearances. One of the basic concepts that all of us are aware of, whether we are cognizant of it or not, is what we see. Humans take appearances for granted. Why? Simply because appearances communicate information that we might not be cognizant of when we receive and process it in our brains. That applies to nearly all animals that have and rely on sight.

But humans also communicate in a myriad of other ways: sound, touch, and smell. Although most other animals also possess these senses, humans rely more on one: language.

Sure, birds and other animals might have their own vocal communications that could be described as rudimentary language. Bird songs and other vocalizations communicate basic intent and even distress, etc. Conversely, human kind has a developed a complex network of language rich with abstract meaning, all which we can hear and see (read). This coincides with our species’ capability of abstract thinking and ability to reason. I doubt that a duck could read and recite the Old English Beowulf and understand it.

Not to be outdone, many animals have evolved complex ways to communicate with their own kind. One example is how they look: different colors or different sizes. Although a few explanations can be posited for differences between the sexes, the most prevalent is mate selection. And the most common expression in birds is differences in coloration between the sexes, called sexual dichromatism. With most birds, but not all, the male is usually the most colorful because they compete for attraction to the females. Thus, sexual selection drives the evolution of chromatic variability.

But how does this work in different species? This is where it gets complicated. Birds can’t write love poems or dress up in fancy clothes, but they can look very appealing with their feathers!

Birds can be sexually monochromatic (same color), where the males and females within a species are the same color year round.

Male & female sandhill cranes.

Familiar examples are most eagles, Canada geese, and sandhill cranes. Most of our bird species in North America are sexually dichromatic; the sexes are divided into two basic appearances. In the latter case, the male is usually more colorful. In some species, especially the shorebirds, the female may be the contrasting sex, called reverse sexual dichromatism (e.g. Wilson’s phalarope).

Some species are extreme in colored plumage. The male may have several very bright and contrasting colors, whereas the female may be drab. These two differences are what most guidebooks depict. Sometimes all the females in an entire genus may look very similar making it difficult to identify which species they belong to.

Male & female Northern flicker

 

But not all mono- and dichromatic species are complete or dramatically colored. Sometimes differences in coloration may be very subtle to our eyes. The male and female red-shafted Northern Flicker look nearly alike except for the absence of the red malar on the female’s face. Similarly, with a monochromatic species, such as the Western bluebirds, both male and female may have the same colors but different saturation. The female’s colors are less saturated than the male’s.

 

Size does matter sometimes.

Size differences between males and females are more present in monochromatic bird species. In larger birds, such as many eagles, hawks and owls, the female is often larger than the male. Size differences can also be subtle, and unless the two sexes are near each other, one may not easily identify an individual as male or female. In other species, such as the sandhill crane and American pelican, there is hardly any difference in size or color and sexing the birds is difficult. But those birds have evolved other ways to communicate between the sexes!

Secondary sexual traits of birds – coloration and size – are varied and most have evolved to communicate attraction and selection. Some traits, however, are driven more by reproduction demands (physiology) than sexual mate selection. Regardless, birds are much more complex than us simply because of need. Perhaps if we never developed a language to communicate, we may have evolved with more extreme sexual differences. Instead, we create our own 😉

Of course, all this is relatively basic and does not tell the entire story about bird coloration. Anyone familiar with ducks knows that most males have more than one coloration plumage during the year. Observers seeing a flock of red-winged blackbirds in the winter might be confused at all the different color combinations exhibited by the birds, thinking more than one species were mixed in together. And then there is the issue of interbreeding subspecies (and even species hybrids!) resulting in a mix of colors imparted by both parents. It can all get very complicated!

My next post will be about the changing of the guard: molting.

Meanwhile, do you have any additional examples of bird coloration?

Turkey Day on the Refuge

27 Nov

As I sit in my ‘home on wheels’ drinking my early morning coffee on Turkey Day catching up on correspondence (and rare Internet connection), I hear the air boat out on the large marshes across the road and RV ‘Village’ on the Refuge. One of the biologists is out this morning picking up dead snow geese. They are carriers of and susceptible to avian cholera. With the prolonged unseasonal cold weather we’ve had here, we’re seeing early mortality of snow geese. I also wonder how much stress levels from extremely high human visitation with the recent Crane Festival adds to increases in mortality rate, possibly compounding overall stress from cold temps, high animal density, lower water volume, and less corn/feed access than in previous years. One of the biologists mentioned last week that recent mortality incidents are earlier than normal.

During the Festival I was fortunate to accompany as an aide a six-hour Sandhill Crane Behavior class. The instructor was crane biologist Paul Tebbel and his associate. Our group of 15 Festival participants was out by one of the ‘Crane Ponds’ in the dark at 5:45am to watch the ‘fly out’. The ‘fly outs’ and ‘fly ins’ are the daily celebratory attractions for people from all over the country as tens of thousands of snow geese and nearly 10,000 sandhill cranes take to the sky in the morning and land in the evening. We chose one of the smaller marshes for a closer and more personal view of the cranes. It was indeed magical and awe inspiring despite temperatures in the mid-20’s. Even the cranes were reluctant to take flight until the sun warmed them a bit. We could see ‘bracelets’ of ice on their legs when they moved around in the marsh.

Paul has been involved in sandhill crane biology and conservation for decades. Formerly the director and manager for the 1400-acre wildlife sanctuary on the Platte River in Nebraska (the bottleneck for sandhill crane migrations), he is now head of the Effie Yeaw Nature Center north of Sacramento. His expertise is crane behavior and he has conducted workshops here at Bosque del Apache Refuge for 20 years!

He is one of the best naturalist instructors I have had the fortune to meet and work with! His casual approach to imparting information on biology and animal behavior elicited a genuine and more personal interest from all participants. I especially enjoyed how he and his associate demonstrated the crane’s pre-flight signals between members of crane family units (forward leaning and looking back to see if other family members and uits were attentive). The two presenters mimicked the crane behaviors accompanied by a human speech interpretation: “Look, Junior, I’m leaning forward now! It’s time to fly! Are you paying attention? Is Mom there, too?”

I learned more about cranes in those six hours than I could ever accumulate from reading literature! And I now have a greater personal and scientific understanding of cranes, as well as an increased overall appreciation of how special they are. Not just because they are ‘big and pretty’ (the most common response to Paul’s question to participants why people are interested in cranes), but also because they have extraordinarily complex social behaviors. And bird/animal behavior is my primary interest (second to biology).

The Festival overall was a huge success for all involved: participants, the Refuge, the Friends of BdA, and the volunteers. It was crazy busy for us all, but well organized. Every single Refuge staff member worked long hours and every day along with the rest of us, and it was truly a great ‘team player’ experience. Even the Refuge Manager was on board daily with smiles and encouragement. All the vendors and auxiliary representatives from public (federal and state) agencies and other non-profit organizations (e.g. wildlife conservation and rehabilitation groups) were tremendously friendly and interactive with both Festival staff and visitor participants.

Now that the Festival is over, all of us get a chance to relax and enjoy more personal time. I volunteered to help conduct raptor surveys every Saturday, which I enjoy immensely. Especially when pointing out one of the bald eagles to visitors that may be around me when surveying the two main marshlands. Folks are thrilled to see them.

I have to admit that I have grown very fond of our smallest falcons, the American kestrels. I was giddy with excitement when close to a rehabilitated female kestrel and a male Great Horned owl (both serve as foster parents!).  Additionally, I now have the opportunity to see many of the male duck species that nest at Malheur NWR in all their winter plumage! One of my favorites is the male bufleheads; they look like large floating black and white Nike sneakers. The only waterfowl missing here from my ‘Favorite List’ is my old friends, the loons. They are a very rare occurrence here.

Since serving the wildlife refuges is my new retirement ‘career’, my intentions are to improve and expand my professional capacities that will enhance my skills and performance as a naturalist and a biologist. This was my goal upon retiring: to devote myself to the conservation of wildlife and contribute to enhancing the connection between wildlife and people. And I admit that doing so is enormously satisfying and often full of adventures.

Our volunteer group here is planning a large turkey dinner potluck this afternoon, including those of the Refuge staff that live on site. Now that we all have more free time I plan to finally take my camera out and hike in the mornings! Although I think I might invest in a pair of insulated coveralls 😉

Happy Holidays to all of you!

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