A studio for bird study

Tag: molt

Plumage in Transition: Red Phalarope Pre-Basic Molt

by Bryce W. Robinson


I don’t often post a large amount of photos from one subject, but I think this bird deserves the coverage. I was birding the western Alaskan coastline with my friends Neil and Ellen the other day when we found this male Red Phalarope – Phalaropus fulicarius. Even better, the bird was mid-way through its pre-basic molt, giving it a unique look. This was the first time I’d ever seen this transitional plumage. REPH_1501

The new feathers of the basic plumage are blue-grey. The old feathers of the alternate plumage are gold and black. It’s a striking difference. Also note the orange body feathers of the alternate plumage, and the white feathers of the basic plumage. These birds are so colorful during their breeding periods on the pools of the Arctic tundra, but after this short period ends they molt into a cool plumage reminiscent of their winter haunts, the open ocean and coastlines. These color changes mean something, or better put, they have context. What a satisfying process, to see a bird in a state like this male and recall that the appearance has a story (begs the question, why the difference in appearance between seasons?).


Although the bird was midway through its molt, it is still identifiable as a male. You can see in the crown that the retained feathers are brown and gold. If it were a female, these retained feathers would be wholly black, and bold. The gold and brown around the face and on the nape also tell its sex.

This bird was so cooperative that I was able to take my fill of photos. It’s rare to see this species in a plumage such as this, so I’m happy that I was able to capture many different angles and views, truly document the bird, and even put the camera down and simply watch. I feel spoiled with the way the birding has been lately here in western Alaska. Too many great things to see, too may things to shoot with the camera, too many experiences to write about. Just the way life should be.REPH_1505REPH_1504 REPH_1507 REPH_1509


Notes on Gyrfalcon Molt

by Bryce W. Robinson

Adult Male Gyrfalcon - Falco rusticolus

Photo 1. Adult Male Gyrfalcon – Falco rusticolus

I like to pay attention to molt in birds. There are many aspects of a birds life history that can be reflected by their strategy for feather replacement. A great example is something I’ve been watching with the nesting Gyrfalcons I’ve been working with lately.

Last summer, I noticed something about the molt between male and female Gyrfalcons. While I was entering nests to install cameras in the early nesting period (mostly during incubation), I noticed that males were behind females in their molt progression. Following my initial observation, I started paying closer attention to each bird. I continue to take notes on this, and wanted to share the molt of a pair from a nest I visited recently.

Adult Female Gyrfalcon - Falco rusticolus

Photo 2. Adult Female Gyrfalcon – Falco rusticolus

You can see that the male (photo 1) has just dropped his fifth primary. Falcons generally begin their primary molt at P 4&5 and progress in two directions. The female (photo 2) has dropped her third, fourth, fifth, and sixth primaries. You can see P 4&5 are growing in already.

This illustrates a few simple things in the life of a Gyrfalcon. One, that energetics govern the ability to molt. Two, that male and female Gyrfalcons have different energetic roles and energy budgets during incubation and early brood rearing. They have different roles in the process. These are illustrated by the fact that they differ in the progression of their molt.

Later, the rates even out as both adults need to provision for their growing brood. I hope to get photos of this pair on my next visit to the nest in a few weeks.

Black Tern in the High Prairie

by Bryce W. Robinson


I think one of my favorite birds is the Black Tern- Chlidonias niger. They are visually striking birds, and their habits are equally intriguing. I remember last summer, making my way down through Canada, bound for the border, then Chicago. Once I hit southern Saskatchewan, the land became scattered with small ponds and marsh lands. It was a lush scene, full of birds. They call these scattered bodies of water on the high prairie the prairie potholes. They are the remnants of the last glacial maximum, and now are home to multitudes of waterfowl, and birds alike.

Black Terns are common in this part of North America. One afternoon, I pulled over at a small pond, where a group of Black Terns were coursing the sky, feeding on the open water. I watched their behavior for some time, and soon realized that they were feeding young, somewhere hidden in the reeds. I could hear the juvenile birds begging. It was impossible to locate a bird. They were simply too deep, safe in the marsh.

At this time of the year, some of the terns had already started their pre-basic molt. It interested me that not all of the birds in the flock had started molting. I know very little about the molt cycle of the Black Tern, but this variation between individuals stuck with me.

I hope to find myself watching Black Terns again, sometime in the late summer this year. If I do find a few, I’ll be paying attention to their plumage, the date, and what aspects might be influencing their individual molt timing. I’m sure someone like Steve Howell, who has studied the various molt strategies between taxa, and knows a thing or two, could offer some insight.


Winter Raptor Surveys- The First Stint

by Bryce W. Robinson

Wintering raptors take precedence above any winter birding, in my book. True, the lakes and wetlands hold an impressive variety of waterfowl and seabirds en route to their wintering grounds, but nothing can be as exciting as the invasion of the bird worlds proudest members. I find feeder watching very rewarding as an opportunity at close range study, however, the birds of prey that populate the agricultural areas throughout the winter months provide easy insight into a world otherwise difficult and distant. Many raptors become docile and tolerant during the winter months as they attempt to conserve their energy with the limited resources they have. Territoriality is dropped, and birds crowd fields, fence-lines, wheel-lines, tree-lines, and roost-sites. Even birds of varying species tolerate one another as they watch for prey.

Last weekend, conducting winter raptor surveys around Beaver and Milford, Utah, I observed a field full of Ferruginous and Red-tailed Hawks. The Red-tailed Hawks mainly rested on a retired wheel-line, but the Ferruginous Hawks seemed to prefer the ground. As I scanned the field and took note of numbers, I observed one Ferruginous Hawk running as a dinosaur might. The bird was in pursuit of some furry creature foolish enough to come above ground. Such behaviors are the reason winter ecology is so intriguing. It seems the birds let go of all reservations to ensure their survival through the harsh and unforgiving months.

HawkWatch International conducts winter surveys every year with the help of a very dedicated volunteer staff of Citizen Scientists. I have been involved in the past, but this year I was asked to take on some part time work conducting winter surveys for a proposed energy development project for the Cedar City Office of the Bureau of Land Management. Currently, northeast of Milford, there is a large wind farm as well as a geo-thermal plant. In hopes of expanding and developing more areas for renewable energy, the BLM has approached HawkWatch International to conduct a comprehensive study of the raptor populations that exist in the proposed areas. The findings from the study will contribute to the environmental impact statement(EIS) that will be necessary for any energy development in the area. I am happy that I am involved in making sure the correct steps are taken before developing lands for renewable energy, and that I am not conducting surveys to help ensure the creation of anything that burns fossil fuels for energy. It all seems pretty moral to me, which is exactly what I want to be doing in my life.

I love the American west, and all of the creatures that inhabit it. Yes, that does include humans, however, it was revitalizing to have a respite from city living, some solitude and satisfying loneliness as I searched for the big cats of the bird world. One thing that the surveys have provided me, and perhaps the most important, is the opportunity to get out and study birds firsthand. In only the first stint of the season, I have already found valuable learning experiences, and my knowledge has grown considerably. It would be foolish not to share what I have learned. so share I shall. The following discussion details identifying age groups in the Golden Eagle, made possible through photographs.

THE GOLDEN EAGLE- Aquila chrysaetos

I came upon a number of eagles in the days I travelled the countryside. Many were in the air riding thermals, but I did have the luck of finding a few birds perched atop power poles. As I have learned more about raptors, I have worked towards honing my identification skills to sex and age, where appropriate. Aging eagles is tricky, but it is a necessary tool for understanding the dynamics of the populations especially in surveys for development. Correctly identifying immature birds from adults is critical for a precise analysis of the status of populations, but I have strived to take it a step further in pinpointing the bird to its relative age. As eagles in general do not gain adult plumage until their fifth year of life, it becomes a challenge to tell the age of an immature bird. I decided to reach out for help from one of the nation’s leading raptor experts, Jerry Liguori. His help has been invaluable.

The Golden Eagle I would like to discuss was a bird I found atop a power pole just north of Milford. I was en route to the geothermal plant on my survey area, but I could not fight the urge to pull over and bother the poor bird. After a few minutes of tolerating my intrusion, the large eagle lifted from the pole. My camera went into action as the bird retreated into the air. My photos have afforded me a few good looks at the plumage of this bird, and the opportunity to analyze and learn what can help me make a conclusive decision in ageing Golden Eagles.

As a general rule, I have always used the presence of white on the wings as an indicator of a juvenile or subadult bird. As I have learned more, I have come to the realization that this criterion has its holes. The presence of white on the wings should never be used as an indicator of age. The certain indicator differentiating an adult from an immature bird is the presence of white on the tail, or the lack of complete adult feather sets. As the bird ages, it staggers its molt. By Year 3-4, or when the bird is in Basic III plumage, it molts its inner and outer most tail feathers creating a dark central band, or split looking tail.

As seen in the preceding picture, the bird I found had a seemingly complete white band on its tail, so it must not have reached Basic III plumage.  Another hint to its age is the presence of the tawny “bar” on the top side of the wing. This bar that comprises the Upper-wing coverts can tell us whether the bird is a juvenile or not. If the tawny bar is lacking, then the bird is a juvenile, still in its first year. This bird has an obvious bar, so it must be in its second year, at least.

The conclusive factors indicating this birds age come from another photo showing the remiges. Assessing molt in the field can be difficult, in reality, nearly impossible, so photos provide the opportunity for a careful look at birds. Look at the primaries and secondaries for any disparities or anything that stands out. Even before I consulted Jerry Liguori, I had picked up on the fact that P9 and P10 on this bird looked very worn.

Often P1-P4 will molt in the first basic molt of the bird, then the next year P5-P8 will fall. The bird retains P9 and P10 into its third year. As the photo suggests, the worn and ragged look of P9 and P10 indicates just this fact. Also, the secondaries will drop in like fashion, and a bird in Basic II plumage may retain S3,S4, S8, or S9. These feathers protrude slightly past the trailing edge of the wing, as they are longer than the newer feathers. The bird I photographed shows this perfectly. S1 and S2 are obviously recessed in relation to S3. S8 and S9 stick out like a sore thumb. Seems conclusive to me. With the help of the camera, and some schooling from Jerry Liguori, I now have a precise identification; An immature Golden Eagle in basic II plumage, a 2-3 year old bird.

I would like to thank Jerry for his help with this discussion. My gratitude and respect is given for those willing to share their knowledge. The world would be nothing without those that are willing to teach.

I will soon be posting about juvenile Red-tailed Hawks, and Merlins.

Till then, happy birding.

B William