Wow! Lots of changes have occurred in the past few weeks since our previous post, the biggest change being the shift in species dominance and abundance. After waiting for first-wave birds to arrive in late April, we saw a major confluence of birds in the first week of May with many species of warbler rolling into the marshes. The number of birds banded daily quickly rose from 100-200 to 300-500 birds, with some surprise birds such as Green Heron, Worm-eating Warbler, Cerulean Warbler, Hooded Warbler, and “Lawrence’s Warbler.” At this point in the season we sit at 31 species of warbler recorded, plus one hybrid.
As great as warblers are though, let’s not forget about the non-warblers. With this great influx of birds entering the marshes, we also had spikes of White-throated Sparrow and Swainson’s Thrush with lesser numbers of Gray-cheeked Thrush, Veery, and Wood Thrush. Despite optimal conditions for major Blue Jay diurnal flights (which can number in the thousands) we have only recorded minimal BLJA movement. However, Baltimore Oriole numbers were quite high with over 20 being banded at the station in one day, coinciding with a diurnal flight tally of over 300 from a nearby Lake Erie shoreline wildlife area. Water levels in the marsh remain at a high level, with quite a few Green Heron hanging around the area. But high water has also brought about more roaming insects and has increased our capture of Tree Swallow (flying low over the water, following midge clusters).
On days with high numbers of birds, we don’t usually have enough time to photograph certain species, sexes, or ages for comparisons. But, when two male Black-throated Blue Warblers of two different ages come in at the same time, we can’t pass on the opportunity to compare molt and plumages!
Determining male in BTBW is fairly simple as hatching-year birds will gain the distinct blue and black plumage of an adult male through their formative molt (replacing their juvenal plumage) in late summer, after they leave the nest (the same holds true for females). By next spring, last year’s hatching-year (HY) bird is now considered a second-year (SY) bird (as it is now in its second calendar year). Differentiating SY male BTBW from after-second-year (ASY) male BTBW comes down to the presence of a molt limit. But even plumage-wise, there are some slight differences. The SY bird is somewhat more matte and shows tints of green compared to the ASY, which shows a much richer, uniform blue back. Also hinting at the age difference between these two birds is the amount of white at the base of the flight feathers - being narrow and mostly limited to the primaries in the SY bird, and wide and extensive across the primaries and secondaries in the ASY bird.
Aside from plumage appearance, the real qualifier for age determination/differentiation in these two birds is the presence of a molt limit. Last year’s HY bird would have molted twice (growing feathers in the nest, and then replacing body feathers and some wing coverts in late summer). This produces two generations of feathers, indicating a limit in the extent of molt. The ASY bird (an after-hatching-year bird the previous year) would have only undergone a pre-basic molt in late summer, producing its basic plumage and a single generation of feathers.
Juvenal feathers are grown quickly and at all once in the nest, resulting in a feather of lesser quality and density that is more susceptible to the elements as compared to a basic feather. Evident in our two BTBWs, the SY bird shows juvenal primary coverts, primaries, secondaries, and tertials that are fairly dull and gray, with limited greenish edging, and contrast with the more recently replaced blue edged, dark centered greater coverts. The ASY bird’s wing shows covert and flight feathers of a single generation that all have a glossiness to them (on account of the more densely barbed feathers), dark gray to black centers, and blue edges (especially in the greater coverts and tertials). Due to this obvious difference between matte gray and dark black, and green versus blue, male Black-throated Blue Warblers are a great bird for learning about molt. This difference is so obvious it can even be viewed through the binoculars in the field!
Another great capture for the station recently was that of a “Lawrence’s Warbler,” one of the two resulting hybrids between the closely related Golden-winged Warbler and Blue-winged Warbler. These two warbler species are so closely related that research suggests their entire genome is only different by 0.3%, making them 99.7% genetically alike. There have even been suggestions of lumping these two species into a single species.
The two hybrid forms are the result of dominant versus recessive genes. The much more common hybrid (“Brewster’s Warbler”) is the result of dominant traits being passed on. While the rarer “Lawrence’s Warbler” is the result of recessive genetic traits, including the black throat of the GWWA and yellow body of the BWWA. Being able to have all three forms in the hand at once (male GWWA, female BWWA, and male LAWA, plus a female GWWA and male BWWA earlier in the morning) was a great way to compare the various traits that are passed down from each parent species and result in the Lawrence's hybrid.
Over the past 50 years, the Golden-winged Warbler has seen one of the sharpest population declines of any songbird species, and is in consideration for Endangered Species classification. The expansion of the Blue-winged Warbler and hybridization with Golden-wingeds has been identified as a contributing factor to the decline in GWWA numbers. However, the primary threat (as well as to a number of other species) is habitat loss both on the breeding grounds in North America and wintering grounds in Central and South America.
It’s the beginning of a new migration season for Black Swamp Bird Observatory’s research team, and we are pumped more than ever to be back out in the marshes of Ottawa National Wildlife Refuge’s Navarre Marsh unit. Daily banding operations were commenced on April 9th, with our outstanding group of volunteers joining the team the following week. It has only been three weeks of banding, but we have already had a pretty interesting season. While the bulk of the data collected at the Navarre station is on neotropical migrants as they pass through the region, data from other short-distance or “winter” migrants is just as valuable and informative. Opening in early April offers us the opportunity to both monitor the movement of early short-distance migrants (such as Hermit Thrush and Myrtle “Yellow-rumped” Warbler) but also track the movements of “winter” migrants (such as Golden-crowned Kinglet, Brown Creeper, and Fox Sparrow). So far this season, we have seen our highest capture rate of Fox Sparrow ever (the station’s highest capture of FOSP in a season was about 40, and we have more than doubled that so far this season). Whether this is the result of a very successful breeding season last year, or was weather induced, is difficult to determine without corroborating data. But it is still a very interesting piece of data to have.
Due to high precipitation and strong north-easterly winds this past winter, the marsh is pretty...well….marshy. Much of the station has higher than average water levels and muck boots are a requirement to reach some of the nets. But due to this high water level, we have doubled another species’ capture record (going from one ever caught, to two captured in a week): Belted Kingfisher. Kingfishers generally don’t enter the marsh too often, but with high water levels near the nets, we were perfectly poised to catch them as they darted through openings in the buttonbush.
Unlike most other species of sexually dimorphic birds, female Belted Kingfishers are more colorful than males (showing rufous-rust streaks along the breast. Unfortunately, much remains unknown about the biology of Belted Kingfisher, with minimal research having been performed (maybe this is due in part to the difficulty of capturing them and their reclusive nature). Along with more BEKI, we are interested to see if these high water levels also bring in other “water” birds such as bittern, heron, sandpiper, and rail.
After an initial deluge of Fox Sparrow, Golden-crowned Kinglet, Brown Creeper, and Belted Kingfisher, the season has been relatively slow. With mostly north and easterly winds, migrants we would have expected to record in higher numbers last week (such as Ruby-crowned Kinglet, Myrtle “Yellow-rumped” Warbler, Western Palm Warbler, and White-throated Sparrow) have only just started arriving in notable numbers this past Friday (which saw southerly winds overnight). This new influx quickly saw the departure of other early migrant species that had been abundant only a week before (FOSP, GCKI, and BRCR). We still have yet to record other typical late April migrants so far this season (such as Black-and-white Warbler and Black-throated Green Warbler), but with southwest winds and warmer temps beginning next week, we are expecting a good movement of first-wave birds and many of the migrants we haven’t seen since last fall.
Text and photo by BSBO Passerine Research Technician, Arthur Sanchez Jr.
A lifer in the hand always makes for a great day of banding! Today we had 130 newly banded birds with 15 recaptures across 17 species. Our captures and species diversity are increasing slowly but surely. In the past three banding days, accumulatively, we have captured and banded 337 birds! Not too bad considering nets have been closed for a few days due to inclement weather.
Text and photo by BSBO Passerine Research Technician, Arthur Sanchez Jr.
This duder was also a great visitor: the first Sharp=shinned Hawk (SSHA) of the season. Ageing these guys in the spring is a little different then ageing them in the fall. We use the same characteristics, molt in the remiges (wing feathers), molt in the upper tail coverts, as well as eye color. But since the ageing system in North America is based on a calendar year system, we have to utilize alternate ageing codes. This is a TY (Third Year) bird, which is not a viable age in fall by BBL standards. This past fall, this SSHA was a SY (Second Year) bird based on the “calendar year” system. After January 1st, this SY bird then becomes a TY bird, or SCB according to the Wolfe Ryder Pyle system.
It’s always interesting to reflect on the banding season once the nets are down and the station is closed up. Each season in the Navarre Marsh is unique, with shifting weather patterns; variations in productivity (number of young produced) between species and even within a given species’ range; minor differences in our banding effort (despite our best attempts to be consistent in this regard); and changes in the microhabitat and overall habitat at our banding station driving annual differences in capture numbers. All of these factors and many more can affect species composition, age and sex ratios, and the timing of the birds we capture. While our capture data vary to some degree between seasons, by banding birds consistently over the long-term we can begin to smooth out the extreme highs and lows in these numbers and better understand overall population trends, as well as variables that affect these trends.
People often envision wildlife populations as stable year after year, but they can more accurately be described as being cyclical and variable around averages or means. As opposed to the idea of consistent homeostasis, a flat line if you will, bird populations are oftentimes better visualized as a dynamic equilibrium, with near continual change – boom and bust cycles that portray population numbers in a wave-like pattern with highs and lows. Across decades, we can also pick up on overall population increases or decreases, age or sex ratio changes, alterations to arrival or departure timing, and other demographic, temporal, or spatial fluctuations. Teasing apart these factors and their effects are topics we’re looking forward to discussing in future blog posts. For now, we’d like to present some of the interesting trends we noticed during the fall season and discuss them in a slightly broader, historical context.
We never catch a lot of these birds during the fall season. In fact, our highest number of captures in a given season is 19 individuals. On average, we band around five Yellow-bellied Sapsuckers each fall. This year, we were close to that average and only slightly above it with six birds banded. What is interesting about this is that last fall (2016) we didn’t band any of these birds. They may have moved earlier in the season (oftentimes birds that fail to breed in a given season will begin to wander or migrate earlier than birds who are tied up in their territory later in the season tending to their young), bypassed our banding station completely, or been present but not captured. With a species that we catch so few of, it’s hard to say exactly what drives these annual differences in capture rate, but in and of itself it’s interesting to merely observe that variability. One way of better understanding the population trends for a species such as this is to compare our annual capture rate with other banding stations over the long term. If capture rates for everyone are down in a given year and everyone’s rates rise in the same year, we can probably safely say that these birds are cyclical in their population trends. Discrepancies in capture rates between stations might indicate more regional or station-specific nuance to bird movements.
Along with Swainson’s Thrush and Blackpoll Warbler, White-throated Sparrow is one of the poster-children of fall migration in the Navarre Marsh. On average we band approximately 350 of these dapper sparrows each fall, but the last two falls have seen us capture far fewer birds than normal with 192 banded this fall and only 158 banded in 2016. These significantly lower numbers could have to do with net height (nets too high off the ground can fail to catch these birds which tend to move close to the forest floor), too many mornings with delayed starts (sparrows are often most active right after dawn, with activity tapering off as the morning goes on), or true population declines. It’s likely that all of these factors are at play to some degree at our station over the last few seasons. Ensuring our banding protocol is consistent and standardized helps us control variation in our effort that may translate to lower catch rate and ensures that the number of birds captured better reflects the true number of birds in the marsh on a given day or in a given season.
Over the last few seasons, we’ve observed a classic cyclical pattern in Blackpoll Warblers, which is typically the species that helps drive our overall numbers each fall season. In an average year, we band around 546 Blackpoll Warblers. We were down from our average approximately 100 birds with 446 banded in fall 2017. Last year, in fall of 2016, we were well above average with 783 individuals banded. Differential productivity in a species that is very prone to population fluctuations in response to spruce budworm outbreaks, a major food source for these birds on their breeding grounds as well as unusual weather patterns, particularly for a species with the capacity to move huge distances in a short period of time, likely explain at least some of the annual variation in our catch rate. With such a large proportion of the world’s population of Blackpoll Warbler moving through the Lake Erie marshes region each fall, maintaining and improving our stopover sites as well as continuing to track this species each year is essential for helping us unravel migration mysteries and overall population trends for Blackpoll Warblers. It’s also critical for ensuring the protection of this species into the future.
This species dominates captures during the early part of the fall season each year. Typically, the peak time for Gray Catbirds in our nets is during the month of August, with numbers tapering off throughout September. With our milder-than-usual fall weather as well as less-than-ideal southwestern migration winds during the bulk of September, we recorded Gray Catbirds at the station all the way up until the last week of the banding season in October. We also captured more Gray Catbirds this fall (366) than our average catch of 278 in a given fall. Numbers of Gray Catbird were also up in fall of 2016 with 343 Gray Catbirds banded. Continued tracking of this species over the long term will help us understand if this represents an actual increase in Gray Catbirds overall and how our local productivity may play into our annual fall capture rates. Because Gray Catbirds nest locally and also migrate through our station, timing as well as plumage characteristics might help us separate out how productive our site is for this species and how productivity in our local area affects overall catbird catches each fall.
The above cases represent only a few of the trend patterns we observe in the birds we study and some of the factors that may affect these species each fall. The importance of tracking these birds consistently, annually, and over the long term cannot be overstated for helping us understand how overall bird populations are faring and what factors affect bird populations. Banding birds gives us reliable and extensive empirical data to this end, data that surveys or field observations cannot provide. By combining our banding effort with consistent survey results, our data become even stronger and more robust, and paint a better, truer picture of fluctuations and trends in the bird populations we so dearly care for. It becomes an essential piece of the conservation puzzle, as only when armed with this basic information can we begin to open the door to conversations about bird conservation.
As we reflect back on another successful fall banding season we give thanks to the birds that provide us a window into the health of our ecosystems and serve to lift our spirits. Scientifically and spiritually, birds take us to new heights and no matter how many Red-winged Blackbirds we see or how many Swainson’s Thrushes we have the privilege of examining up close, we never lose sight of how important these individual birds are to birders, researchers, and the ecosystems we work to protect.
Following a week of warm southern winds, we were excited for a weather shift last week, that would bring cold winds down from the north. While we were expecting to see a final bump of late-September migrants that we hadn’t seen yet (specifically large numbers of Blackpoll Warbler), we were quite surprised to get a wave of October migrants including our 25th warbler species for fall, Myrtle Warbler. Since that wind shift, we have seen a quick rise in Slate-colored Junco, White-throated Sparrow, Yellow-bellied Sapsucker, Winter Wren, both kinglet species, Brown Creeper, Rusty Blackbird, and Hermit Thrush.
Often caught singly just before dawn, we were extremely lucky to catch TWO Eastern Screech-Owls of different ages (and colors!) together in the same net (presumably parent and offspring), offering us a great opportunity to compare age specific characteristics. While the young bird is a gray morph, the (presumed) parent is an intermediate/brown morph and was banded in a previous season. Coincidentally enough, both birds' band numbers end in 61.
Based on appearance alone, it's fairly obvious that the gray morph EASO is a hatching-year bird. It still has some remaining juvenal feathers, giving it a somewhat fluffy but also ragged look compared to the after-hatching-year bird which has a smooth appearance. This difference is most noticeable in the ear tufts (which are not fully grown-in on the HY bird), and the facial disc (which is smoother and more complete on the AHY bird).
Aside from looking just at the head feathers, we were able to accurately age these EASO’s by looking at the alula feathers and primary coverts in the wing. Just from an immediate glance, you can already see that there is a difference in the amount and shape of light areas in the wings of these two birds.
White/cream areas on the alula and primary coverts help to determine age. The HY bird on the left shows these areas as small jagged triangles on the edge of the feathers. Whereas the AHY bird on the right has larger, rounder, and often connected triangles (especially on the outer primary coverts), giving the wing a lighter appearance.
But by far, the coolest bird we were able to work with recently was a first-ever capture for the station...Wilson’s Snipe. While we do occasionally catch American Woodcock, we don’t regularly see shorebirds in the station, so the snipe made for an exciting and educating morning.
Combing through our Pyle II guide, we found that aging and sexing Wilson's Snipe is pretty easy. Shown with the figure in Pyle, you can look at the tipping and shape of the greater coverts to determine age. In this case they are square, white, and several of them have characteristic notches (such as figures C and D) that indicate the bird is after-hatching-year. To figure out the sex, we had to look to the outer rectrices. Next to the figure in Pyle, it’s plain to see that the outer rectrix is fairly wide and rounded just like figure A, indicating female.
So....our first ever Wilson’s Snipe was accurately aged and sexed as an after-hatching-year female. After we determined the important stuff, we took a little time to examine and appreciate the other features of this bird and we also learned something new...Wilson’s Snipe have zebra underwings! Whether you’re out birding or banding, keep an eye out for these hidden vermiculations.
Within a short period of time, we quickly went from banding 20-30 birds a day, to processing 70-100 birds daily. However, with recent hot weather (temps in the 80’s over the past week) our numbers have dropped back down to about 40-50 birds daily. By the end of this week, with temps cooling down and winds coming out of the north, we should really start to see some good numbers as we head into the heaviest part of migration. Our warbler count is up to 24 species now and we have begun to see more diversity in migrants. But the largest bumps in numbers have come from Swainson’s Thrush and Blackpoll Warbler (two of our most dominant fall species), catching (so far) anywhere from 15-40 of each species a day.
At this point, Baltimore Orioles and most of the flycatchers have completely left the area, and even though they SHOULD be gone, we have caught a few late Prothonotary Warblers. Along with new thrushes and warblers coming in, we have also banded a few Ruby-crowned Kinglets and a (gorgeous) White-throated Sparrow, and have heard Golden-crowned Kinglet and Red-breasted Nuthatch in the station (sure signs of fall). There have also been a few great surprise captures over the past couple of weeks including a hatching-year (HY) male Golden-winged Warbler.
While the mist net mesh size we use is suited best for smaller passerines, we do on occasion catch larger birds (if we can get to them fast enough before they bounce out of the net). Case in point, we were at the nets just at the right time to capture an HY female Cooper’s Hawk this past week.
Aging accipiters is pretty straightforward. A yellow eye, brown back, and white chest with vertical brown streaks distinguish this bird as an HY (versus a red eye, blue-gray back, and horizontal orange streaking in an adult). While there is some overlap in measurements between the sexes, determining female from male is also pretty easy, with females being significantly larger than males (this female weighed in at 457 grams).
Not necessarily a surprise capture (as we banded a significant amount of them) Magnolia Warbler is a great starter species for learning how to age and sex other Setophaga warblers. First, look for a molt limit in the wing to age the bird. In the bird pictured on the left, there is an obvious difference between the retained narrow, brown-gray juvenal primary coverts (p-covs) and alula, and the newer, black greater coverts (gr-covs); making this bird an HY. The
after-hatching-year (AHY)(adult) bird pictured on the right lacks a molt limit, showing similarly colored gr-covs and alula feathers, and wide, dark gray p-covs. Also note the AHY's wide, truncate tail feathers compared to the HY's relatively narrow tail feathers in the lower middle picture.
After age is determined, figuring out the sex pretty much comes down to three things: streaks, upertail coverts, and white in the tail. Even in both age groups (HY and AHY), males will typically show more of each of these features than females (ie. more prominent black streaks on the sides, breast, and back, more black in the upertail coverts, and more white in the tail). Looking at our two birds, you can see that the sides have distinct black streaks (especially on the AHY), the upertail coverts are overwhelmingly black, and there are large, similarly sized spots of white throughout the tail feathers (except the center two). Also note the AHY why has some flecks of black in the face. Combined, these three features confidently make the right HY and left AHY both males.
Starting August 14th, the Navarre Marsh Banding Station has been operating nearly seven days a week, sampling migratory birds as they pass through the marshes of western Lake Erie. It’s only been a few weeks, and migration is still quite slow, but boy have we seen some great birds come through the station already! Beginning with a surprise Kentucky Warbler on the first day of banding, so far our warbler list has reached 21 species for the fall season, including Connecticut, Canada, Mourning, Blackburnian, and Chestnut-sided. Not too bad of a start for the beginning of September. Aside from warblers, in our first few weeks we’ve also begun seeing hints of other migrant families represented by Veery, Gray-cheeked Thrush, Swainson’s Thrush, Philadelphia Vireo, and Yellow-bellied Flycatcher.
It may seem early in fall migration, but birds are moving, and many of the marsh’s summer breeders have already departed. Yellow Warblers are entirely absent, and Prothonotary’s have become few and far between. Staging Baltimore Orioles are drastically reducing in presence, and Gray Catbirds (abundant only a week ago) are slowly filtering out. But while others are departing, and some are trickling in, flocking species such as Common Grackle and Cedar Waxwing continue to stage along the lake shore, building in numbers every day.
While every bird that passes through the station is incredible in its own way, there have been a few birds recently that really caught our attention. The first being an aberrant plumaged Gray Catbird (hatching-year, full juvenal plumage, affectionately termed the Glaucous Catbird) with an apparent melanin deficiency. While most pigment aberrations seem to affect only the feathers on the majority of birds, the interesting thing about this catbird was that every body part color was subdued. Body and flight feathers, beak, legs, and eye color were all a paler color than found on a typical individual. Photographing subtle colors can be difficult, so to try to make the pale color obvious we photographed a normal catbird of the same age shortly after the paler bird in the same lighting.
Nearly a week after our first encounter, the pale cat was recaptured with slight signs of body molt. Limited mostly to the crown, the incoming feathers (which would typically be black) appeared to be coming in as a dark brown color. It’ll be interesting to see what this catbird looks like after it completes its molt. Hopefully it’ll stick around a little longer or come back in the spring to offer us a glimpse at its incoming plumage.
An unusual visitor for the fall, a hatching-year Olive-sided Flycatcher stopped by this past week, exciting our team and drawing our attention to the plumage characteristics of young flycatchers.
Hatching-year flycatchers are easily distinguished from adult birds by the presence of buff tipping to feathers and buff-cinnamon wing bars. This is especially true among the Empidonax flycatchers who show whiter wing bars as adults, in addition to other species who don’t show wing bars as adults, like Eastern Phoebe .
For whatever reason, we don’t often see Eastern Wood-Pewees in juvenal plumage, even though it is a local breeder. But the very next day after catching the OSFL, we then caught a hatching-year EAWP, still mostly in juvenal plumage. These two species are members of the genus Contopus, so catching juveniles of each was a great way for us to focus on a new group of flycatchers other than Empids. For a bird that will eventually molt in green-gray feathers, it was interesting to see the extent of buff-tipping to the majority of juvenal body, as well as the wing covert feathers in the EAWP. These buffy wing bars in the EAWP will be white in an adult bird. Also a hatching-year (but further along in molt), the OSFL only showed the slightest edging to remaining juvenal feathers on the back, as well as distinct pale wing bars. These wingbars will be narrow or non-existent in adult OSFL. One very interesting detail we noticed on both of these birds was that the buff/pale edge of these juvenile feathers is even evident at the tips of the flight feathers and tail feathers of both of these closely related species.
It may be hard for some to accept, but FALL MIGRATION has already begun!!! (Sorry summer). In preparation for our fall migration banding season in the Navarre Marsh Unit of Ottawa National Wildlife Refuge, our research team has been hard at work the past week clearing lanes, trimming back grapevine, and setting up nets for the new season before our volunteers arrive. With an official start as of yesterday, the season has already started off in a great way. Being only the second capture record for fall in the history of the station, our team was ecstatic to catch this hatching-year male Kentucky Warbler.
Regarded more as a "southern warbler," Kentuckys are uncommon to rare in NW Ohio during spring migration, let alone fall. We'll never know where this bird came from (maybe Oak Openings, maybe Michigan, or maybe he just wanted to fly north before fall). But we do know that he visited Navarre Marsh.
Whether or not this represents a northern expansion of the species is impossible to say. Only further years of research will be able to determine that. But for now, it represents a remarkable encounter and the knowledge to be gained from science.
Stay tuned during fall migration for our daily banding updates and follow along to find out what our research team is hearing, seeing, and banding in the field. You can also support our research team's efforts by sponsoring a mist net.
Blink and you'll miss it! Ryan Jacob, one of BSBO's research staff, measures a hummingbird band. Get in close enough and you can read the unique number printed on each band, helping to give each hummingbird we band its own identity.
Ryan and BSBO's Banding Projects Manager, Ashli Gorbet, depart tomorrow morning for hummingbird banding training in Texas, where they'll expand their knowledge of all the VERY fine details of handling, aging, sexing, and banding these tiny miracles.
If you wish to lend your support to help cover the costs of travel and training, we would greatly appreciate your help. Just click here http://www.bsbo.org/donate.html and donate through our secure website.
Ryan Jacob, Ashli Gorbet, Mark Shieldcastle