25 November 2010

Twitching the Colorado Ross's Gull

On Friday, 18 November 2010, I got an email from the Kansas listserv with “Extralimital Ross's Gull” as the subject. As I began reading the report my mind started to race, thinking about the arrangements that would have to be made in the next 24 hours. It wasn’t a question of am I going to twitch this one, but rather, how am I going to twitch this one. When I found out the bird was being seen in Colorado outside of the Denver area, I thought it would have to be done by airplane. I soon scratched the airplane idea as the cheapest ticket was $419 for a next day flight. Googlemaps estimated a oneway trip to be roughly 16 hours. Piece of cake.
The bird was found Friday morning by Joe Roller who originally ID'd it as an adult Little Gull but later concurred with a Ross's Gull ID made collaboratively by himself, Glen Walbek and Cole Wild. The ID was confirmed that same afternoon. The photos were released and this, more than anything, drove me over the top. I waited it out and followed the updates for the next 6 hours. I made a post on the Illinois Birders Forum to inform birders of this rarity. Bruce Heimer, who I knew would be the first to call me, called and left me a message the next morning with these being his first words, “Dude, the bird is still being seen”. No clarification was needed for “the bird”. Bruce was one of the 5 birders who joined me for the Cape May Ivory Gull twitch just 11 months prior. On the ride home from Cape May we explicitly said to one another that a Ross’s Gull would warrant similar actions.

On Saturday, 20 November - less than 24 hours after the initial report - we finalized our plans and were able to enlist Greg Neise, Chris West (probably one of the most active and talented ABA birders in his age bracket) and both of the Gyllenhaal brothers – Ethan and Aaron. This was a very bizarre chain of events as Chris, Ethan and Aaron had also been on the Ivory Gull twitch with us. Meeting time was at my house at 8:00 p.m. Bruce was responsible for picking up Greg, Chris was on a 3.5 hour trek from his home state Wisconsin and the Gyllenhaal brothers were being dropped off by their father Eric, who coincidentally joined us on the Ivory Gull twitch, but sat this one out. All parties magically united on time.
We were pulling out of my driveway at 8:03 p.m. We got about ½ block away when someone asked, "did you bring the bread"? I knew I was forgetting something. I made a U-turn, pulled into my driveway, ran inside the garage and grabbed 2 garbage bags full of my emergency stash of stale bread. Off we go! We hit the road and got there in 13.5 hours. The trip was as smooth as can be - it always is on the way there and this must have something to do with all of the positive energy of a hopeful twitcher. For some strange reason, I insisted on driving the entire way. This was also the case with the Ivory Gull twitch. I don’t plan this extreme and irrational behavior but something seems to compel me. About half way there, I say to myself, “you’ve driven this far, just finish it off”. I’m not sure if it’s my fear of letting others drive or subconsciously not relying on others to get me to my birds. My wife says I feel the need to work for birds of this magnitude and so that’s the explanation I’m going with.
We got to Cherry Creek State Park around 9:00 a.m. on Sunday and got news from local birders that the Ross's was seen a little while ago on the northwest side of the lake near the marina. We set up on the beach just south of Dixon Grove on the northeast side of the lake with the sun to our backs. We began to scan. I spotted an adult Lesser Black-backed and got a little giddy about that. Then I spotted a loon which I was pretty sure was a Pacific Loon. “Chris, check out this loon in my scope”. Chris confirmed it was a Pacific – a lifer for me that held no significance at the time. I needed to stay focused. “Oh, there’s a California Gull; and another one”. I told myself to keep my eyes on the prize. “Greg, is this a Thayer’s Gull?” STAY FOCUSED!
After about a half-hour of scanning with a group of about 12 birders, I finally spotted it: “I GOT IT”!!! Birders demanded a location. I was lost for words. I was still trying to internalize that I had the Ross’s Gull in my scope. At first glance, I noticed a bird about the size of a Bonaparte’s Gull with a noticeably peaked head. The image that keeps replaying in my mind is that of a small white-winged gull on the water next to an adult Bonaparte’s. The difference in wingtip color is - and should be - noticeable to anyone who is familiar with Bonaparte's Gull.  “It’s on the water with a Bonaparte’s to its left. They’re swimming between two...what are those white tubes called that float in the water?” Buoys! “Yes, it’s between the two white buoys against the opposite shore. Wait, it's moving. It's up”! The Ross’s began to fly around with what seemed like no purpose in mind. It put down shortly after and everyone got on the bird. The ID was obvious. We debated whether or not we should hurry over to the other side of the lake but decided to wait about 15 minutes to see if the bird would come closer to us. We soon gave in and made the drive around.
We parked at the marina on the northwest side of the lake. Bruce and I made a run for it as we could see the bird standing on the famous sandbar that it made its resting station. We can see people enjoying great looks but it got up and took wing before we can reach the sandbar. It began to circle and maneuver similar to how a Bonaparte’s flies but there was something much more intriguing about this bird. It was a Ross's Gull on a small lake in Colorado! It was almost like it knew it was being watched by everyone on the lake, even by the other gulls. I walked out a distance to the east on the dam road in order to gain better lighting. It spent most of its time over the center of the lake, circling and feeding at the water's surface. It was harassed by a couple of Ring-billed Gulls and then it positioned itself in the middle of a group of Western Grebes as if to take refuge among them. It then got up again and continued to randomly work the edges of the lake. At one point it lazily flew along the northern shoreline giving Aaron and I great looks as it came within 25 yards of us.
Basic Adult Ross's Gull, Cherry Creek State Park, Colorado; 21 Nov 2010

I started to pick out important ID marks that I had reviewed the day before. Big eye on a smallish head with a short stubby bill? Yes. Grayish underwings (not black like Little Gull)? Yes. Pointed wingtips with a long hand? Yes. White secondary bar that tapers off at the mid-primaries? Yes. Observation time was short and I must admit that one thing I forgot to look for was the wedge-shaped tail. This mark is a great ID point in all plumages. Suddenly the bird began to circle back and it gave Aaron and I another close look insomuch that we could see the pink suffusion on the underparts with the naked eye.
We watched the bird for perhaps under 3 minutes at this distance when suddenly it did something very unusual. It began to ascend and circle over the lake in a manner that suggested it was going to depart. It did this twice in the course of 15 minutes and so people began to panic. In my heart of hearts I thought I watched the bird put down towards the south side of the lake and that was the last I saw of it, but I was told people watched it land on the west side of the lake, south of the marina. We decided to get back in the car and find a better vantage point from the Lake Loop parking lot. As we were getting out of the car, I commented to the group about how the sky had become very overcast and that the winds had shifted. A cold front quickly swept in and the lake began to fog up. In less than 30 minutes the entire lake looked like a scene out of Michael Jackson's Thriller video. Here is a before-and-after of the conditions on the lake. This transformation took place in the course of an hour:


The "after" photo is not in black-and-white. This is the actual color of the lake presented by the rapidly changing conditions. We started to brainstorm and thought this would be a perfect time to bring the gulls to us. Bruce brought along a few bottles of cod-liver oil that we smeared on the bread. We made our way back to the eastern shoreline and we began to chum in the gulls. We had a nice assortment of California Gulls with the highlight being an adult Mew Gull that I picked out - but no Ross's Gull.

 Adult Mew Gull (center) with California Gull and Ring-billed Gulls.


We had no solid strategy as this was the first time the Ross's had gone unnoticed for an extended period of time in the last 3 days. We made it back to the Lake Loop area and ran into a group of birders who also felt the gull had departed. One birder told us the gull was reported at 12:05 p.m. Naturally, we got our hopes up but we came to find out that this report was from yesterday...oops. As a spoiled Illinois birder, I felt the level of communication by the immediate Colorado birding community was lacking. I say this because an ABA Code-3 bird should be reported with much more detail and frequency. For instance, many reports were vague with phrases such as "bird is being seen right now". Often, no specific vantage points were suggested nor were times included in the text of the report. It should be noted that Yahoo groups are notorious for not updating correct times with their posts and so this adds to the confusion of trying to get concise reports. 

Just as fast as the weather conditions had worsened, the weather began to change and viewing conditions became ideal. The lake became calm and clear. We thought this would be our best opportunity to refind the gull. We scanned and scanned, and scanned but alas, no Ross's. Nothing but a few Bonaparte's off to the opposite shore which made for a great exercise for anyone who wanted to really reinforce the distinguishing ID marks of Bonaparte's and Ross's Gull. This was in fact the most educational part of the trip for me. 
Swim Beach looking north towards dam
More than 3 hours had passed and there was no trace of the bird. We had pretty much lost hope. Finally, after a nagging suggestion by one birder to go hit a few country roads in search of Ferruginous Hawks, I gave in. We ran into Ira Sanders (brother of long time Chicago birder, Jeff Sanders) who gave us spot-on directions for Ferruginous Hawks and Prairie Falcons. Bruce suggested that we should try the eastern shoreline one last time and we did. Nothing but Bonaparte's, Californias and the single Mew Gull. We packed up and made the 1+ hour trek to find "Ferruginous Hawks". We were successfull with 3-4 FEHAs in less than 15 minutes. We also spotted a Prairie Falcon and multiple Western Red-tailed Hawks. The sun was beginning to set and it would soon get dark. We then punished ourselves by checking the Colorado list where we read a report explaining how birders were currently enjoying good looks of the Ross’s Gull close to the dam. We were over an hour away and it was impossible to make it back to Cherry Creek S.P. before sundown. A few of us doubted the report was current but it was. The bird had been relocated and we weren't at the lake! We left the lake when we should have committed ourselves until sundown. You live and you learn. Where was the Ross's Gull hiding this entire time? One report explained that the gull took to the southeast side of the lake during the storm. This makes sense as it would have been protected from the winds that ripped through. Truth be told, this is the only section of the lake that went neglected by us due to inaccessibility.

The bird was seen by all of us and admittedly I probably enjoyed the best looks, but I've concluded that Ross's Gull is "unfinished business" for me. You might ask, what is the price that was paid for this bird: 2,058 miles and 36 hours! For some, seeing a Ross's means checking it on a lifelist and moving on. This is far from true in my case. In due time, I will have to exert more time and energy on this species. An adult in alternate plumage would be wonderful but I long to see a juvenile Ross's which is very unlikely to occur in the United States. I do feel that I will never treat a flock of Bonaparte's Gulls as just "Bonaparte's". Both Howell and Olsen mention that Ross's, just like Little Gull, are more times than not found with Bonaparte's Gulls when out of range. 
 Left to right: Aaron Gyllenhaal, Greg Neise, Bruce Heimer, Chris West, Ethan Gyllenhaal, Amar Ayyash
  As of 25 November, 2010, the Ross's Gull is still being seen at Cherry Creek S.P. The lake has risen slightly and the sandbar isn't visible anymore. Coincidentally, the Ross's has been reported on the south side of the lake near a few large stumps. This should be great for photographers as the sun is now at their backs for most hours of the day. Oh, would that I were a Coloradan today!
The best photo I've seen of the Cherry Creek Ross's Gull. By Robb Hinds; 25 Nov 2010

07 November 2010

Preformative Molt and Bonaparte's Gull

It is said that molt is the most understudied and underappreciated aspect of birds. Maybe. I remember reading a paper by Peter Pyle a few months ago where he mentions how it took him something like "ten years" just to wrap his mind around molt terminology. Wow! Over the last two years, I've come to appreciate this bewildering subject and a basic understanding of the "modified" Humphrey-Parkes system has helped me understand birds just a little more. A deeper understanding of molt becomes integral when considering gulls and, becoming familiar with the various molt strategies is a requisite for anyone with a veritable interest in this family.

Birds molt at different rates and frequencies but all generally follow one of four strategies. Determining which molt strategy (Simple Basic, Complex Basic, Simple Alternate or Complex Alternate) a bird obeys depends almost entirely on the events that take place in the first cycle.

Of the four molt strategies, the Complex Alternate Strategy (CAS) is, to me, the most unique. I have a particular interest in this strategy because it applies to all of the hooded gulls that occur in North America. Here, a formative plumage and an alternate plumage are found in the first cycle. These plumages are a result of a partial preformative molt and a partial prealternate molt. Most birders generally know what is meant by a prealternate molt but I've found that many don't know the implications of the "preformative molt". In the past, ornithologists (including Humphrey and Parkes) overlooked the preformative molt and called it the first prebasic molt (Howell, 2010). The juvenile plumage was not point zero in the study of molt and so the former approach was easily justifiable because formative plumage can resemble that of a basic adult (Howell and Dunn, 2007). However, the preformative molt and prebasic molt are two different events. The modified H-P system suggests that a bird has arrived at 1st basic when in juvenile plumage. That is, the "1st" prebasic molt produces the juvenile plumage. The preformative molt is an additional molt that follows but is still contained in the first cycle; Unlike prebasic molts which reoccur, there are no preformative molts in any cycle thereafter.  Howell describes the preformative molt as a one-time event that acts as a "bridge" from juvenile plumage to 2nd cycle.

A good example of a common species that acquires formative plumage is Bonaparte's Gull. There are generally two waves of first cycle Bonaparte's that are observed in North America after the breeding season. The first wave begins in late July to early August and it consists of juveniles that appear to be in mostly fresh plumage like this individual:

Juvenile Bonaparte's Gull before acquisition of formative plumage; Chicago IL, 15 AUG 2010

By the end of August, these individuals become harder to detect because the preformative molt soon changes their appearance. The second and more significant wave of Bonaparte's typically peaks in late October (depending on migration routes and wintering latitudes). The first cycle individuals in this wave have concluded, or have come close to concluding, the preformative molt: 


 First cycle Bonaparte's Gull in formative plumage; Chicago IL,  2 NOV 2010

Some obvious changes have occurred but note that the juvenile flight feathers are not replaced as this is a partial molt. The juvenile tertials are still evident but much of the the upperwing coverts have become worn. The head, neck and sides of the breast lose the brownish wash of the juvenile and this is a result of the body feathers molting. The brownish mantle and scapular feathers have also been replaced by the partial preformative molt. The bird now has an overall adult appearance. This is the stage that Humphrey and Parkes would have called 1st basic. If you're familiar with Jon Dunn's Advanced Video Series, then you'll note that the video on "small gulls" doesn't refer to juvenile plumage as 1st basic. It also fails to make mention of formative plumage as these videos predate the latest modifications to the H-P system. Again, a juvenile is equated with 1st basic in the modified H-P system. Although the replacement of some feathers occurs, the preformative molt should not be considered as "the" gateway to 1st basic. This is a distinction that needs to be made when considering Complex Basic and Complex Alternate.

Same juvenile as first photo. Note the cinnamon-brown subterminal edging to the median/greater coverts. These upperwing coverts are not molted in the partial preformative molt. The November individual above with almost entirely gray median/greater coverts has the same upperwing coverts it had in juvenile plumage. Only now, the brown coloring on most of the coverts has faded on all but the lesser coverts; This is why a carpal bar is still evident in flight on individuals in formative plumage.  

First cycle Bonaparte's Gull in formative plumage; Carlyle IL; 14 NOV 2010


A slightly darker than average individual in formative plumage.  Note the juvenile wing and tail feathers produced by the 1st prebasic molt. The adult-like mantle and the white body feathers are a result of the preformative molt. In late winter, this species begins its 1st partial prealternate molt - a reoccuring molt in subsequent cycles.

I found the slightly longer tail feathers very interesting on this individual. Is this surplus in length needed since the central tail feathers act as coverts on the closed tail?


I hope to follow up on this post with an explanation of the rest of Bonaparte's first cycle when it undergoes the first prealternate molt. Meanwhile, I'd like to recommend a few resources for anyone wishing to pursue this subject in more detail:
  • All You Ever Wanted to Know About Molt But Were Afraid to Ask, Part 1 (Birding, October 2003,pp. 490-496).
  • All You Ever Wanted to Know About Molt But Were Afraid to Ask, Part 2 (Birding, December 2003, pp. 640-650).
  • Gulls of the Americas; Howell & Dunn, 2007.
  • Identification Guide to the Birds of North America, Part 1 & 2; Pyle, 1997, 2008  
  • Molt in North American Birds; Howell, 2010.
I'd also like to leave you with one final thought that Steve N.G. Howell mentions in his latest work on molt: "We must accept, however, that even the most elegant human systems are imperfect attempts to put dynamic natural processes into boxes. There will always be exceptions. It is human nature to focus on exceptions, but to understand patterns it may be more helpful to focus on features shared by the majority of birds" (Howell, 2010). What if one day the modified H-P system is itself modified to include the prejuvenile stages?