[obol] Re: Vagrant Bird Behavior

  • From: Wayne Hoffman <whoffman@xxxxxxxx>
  • To: David Irons <llsdirons@xxxxxxx>
  • Date: Fri, 10 Mar 2023 14:56:32 -0500 (EST)

Good thoughts - 
In the 4 years I have been here in North Carolina, there has been a pretty good list of western vagrant land birds, but certainly not the kinds of numbers that coastal California sees for easterns.
Off the top of my  head in these 4 years,
Black-chinned HummingbirdRufous HummingbirdRufous X Anna's HummingbirdAsh-throated FlycatcherPacific Slope/Cordilleran FlycatcherHammond's FlycatcherGolden-crowned SparrowMountain BluebirdMacGillivray's WarblerTownsend's WarblerAudubon's (Yellow-rumped) WarblerBlack-throated Gray WarblerWestern TanagerBlack-headed GrosbeakLazuli Bunting
A "Nashville" warbler has wintered near Raleigh this year, and locals are convinced it is actually a "Calaveras" Warbler, the western version.  A Wilson's Warbler wintering here in Wilmington this year appears to be the northern/eastern subspecies, but one that wintered 2 years ago looked more lica a Pacific Coast bird.
Wayne

From: "David Irons" <llsdirons@xxxxxxx>
To: "obol" <obol@xxxxxxxxxxxxx>
Sent: Friday, March 10, 2023 1:52:34 PM
Subject: [obol] Re: Vagrant Bird Behavior

Hi Wayne,
I just wanted assure you and others that I was in no way put off by your response to my post. I didn't want my initial comments in the earlier response to be misconstrued. I fully expected and even hoped that someone would come forward with some exceptions to my answers. There is so much ground to plow that it is impossible for any one person to have all, or even some of the answers. While the eastern songbirds to the West Coast dynamics seem reasonably well understood, and evidence that DeSante mirror-image theory applies elsewhere on the globe, there are many other mechanisms that factor into vagrancy. Weather surely plays a role in re-routing Sibe passerines, shorebirds, and waterfowl down the east side of the Pacific. This is one case where the idea of birds being "blown off course" applies. 
Another question to ponder is this, are the western songbirds that occur during fall and winter across the eastern half of the continent also mirror-image misoriented? The raw numbers of western birds east is far lower (based on detection rates) than the numbers of eastern birds coming west. I suppose the first part of the answer would be to compare the estimated raw population numbers for the respective species. The variety of eastern warbler species (and likely individuals) far surpasses the number western species and probably individuals. Then there are the shared species like Orange-crowned and Wilson's Warblers that could be producing the stealth vagrants. Do lutescens and orestera Orange-crowned Warblers or pileolata and chryseola Wilson's Warblers occur on the East Coast and if so, who will notice other than maybe banders? 
Perhaps the one exception to vagrant imbalance (generally favoring the west) is the Empidonax flycatchers. If you take Least Flycatcher off the table because its breeding range extends so far west and southwest, the west gets far fewer stray Empids than the east. Again, we are looking at an imbalance in the number of potential species that could stray. Who knows how many eastern Willow Flycatchers come west and how many western Willows go east and Acadian Flycatchers are either going undetected, or they just don't come west with any frequency. There also seems to be far more records of "Western" Flycatchers east than there are Yellow-bellied Flycatcher records for the west, but it's impossible to know how many we miss. I don't have the new Birch and Lee "Field Guide to North American Flycatchers," but I am seeing that some already have it in their hands. I assume that they delve into some of these questions and presumably the mirror-image vagrancy of southern Hemisphere and tropical flycatchers and kingbirds. I look forward to getting that book. 
Dave Irons Beaverton, OR 






From: obol-bounce@xxxxxxxxxxxxx <obol-bounce@xxxxxxxxxxxxx> on behalf of Wayne Hoffman <whoffman@xxxxxxxx>
Sent: Friday, March 10, 2023 3:42 PM
To: obol <obol@xxxxxxxxxxxxx>
Subject: [obol] Fwd: Re: Vagrant Bird Behavior   OOPS M ake that winds from Northwest to southeast
From: "whoffman" <whoffman@xxxxxxxx>
To: "David Irons" <llsdirons@xxxxxxx>
Cc: "obol" <obol@xxxxxxxxxxxxx>
Sent: Friday, March 10, 2023 8:03:44 AM
Subject: [obol] Re: Vagrant Bird Behavior

Hi, Dave -
Excellent, high-information-content post.
I have one comment relative to Eastern Yellow Wagtails, and another about songbird migration that comes from pelagic trips I took off Florida back in the1970s and 1980s.
DeSantis' reverse migration explanation for eastern songbirds appearing in the west is pretty well accepted.  It also seems to apply to long-distance vagrancy of Neotropical tyrant flycatchers. 
However, in Howell, Lewington, and Russell's book "Rare Birds of North America" the authors give a different explanation for Asian landbirds reaching the west coast, which might apply to wagtails, as well as Dusky Warblers,  Willow Warblers, Red-throated Pipits, and several other species.  These are species in  which populations breeding in the far northeastern part of the range, in eastern Siberia or even western Alaska, normally migrate southwest across the ocean past Kamtschatka towards Japan.  According to them, if these birds encounter severely unfavorable winds, they apparently fight against it for a while, then give up and then turn downwind, and just ride the wind.  Likely many run out of energy and drop into the water, but a few manage to make landfall on the west coast.  A number of occurrences of these birds in fall have been associated with weather patterns in which the north Pacific  was dominated by strong winds blowing from Northeast to southwest.
Back in the late 1970s and 1980s i lived in Florida and took a few early fall pelagic trips off the east coast.  We commonly encountered groups of migrating warblers on these trips,  The ones we saw (in daylight) were flying within 100' of the surface (we would have missed any higher ones).  They were in loose aggregations, where they were clearly in contact with each other but spread out too far for any aerodynamic benefit.  Someone on board would yell warblers, and we would all start scanning.  Someone would yell Black-throated Blue, the next person Cape May, the next Redstart, maybe the next waterthrush.    So these birds, which we are taught migrate at night do often take overwater flights that last longer than a night, and of course continue flying on through the next day.  And, at least in the daytime they tend to travel in mixed-species groups.
Wayne

From: "David Irons" <llsdirons@xxxxxxx>
To: "obol" <obol@xxxxxxxxxxxxx>
Sent: Thursday, March 9, 2023 9:58:38 PM
Subject: [obol] Re: Vagrant Bird Behavior

Tom,
Not all of your questions have easy answers and some of my responses my be unsatisfying.
#1 Why is the Gray Catbird here? Hard to know. The sample size for this species overwintering in Oregon, or anywhere along the West Coast is pretty damn small, thus not revealing much of a pattern to study. As noted in my previous email, the "mirror-image" migration theory put forth by Dave DeSante is pretty widely accepted as an explanation for how so many "eastern" songbirds end up in the west during fall migration. The real question has always been why? I've heard it suggested that this may be a survival mechanism of sorts, with off-course birds being viewed as "pioneers" spit out by the genetic tumblers to go the wrong way in order to populate new areas, thus protecting the species from disappearing due to some more localized combination of events in its home range. I don't know how one would go about trying to prove this theory, but it seems plausible. Who knows why it this bird stopped where it did. Gray Catbirds do migrate earlier in the fall (August/September/October), so it seems likely this bird had been present for some time (months) before it was first discovered by Colby Neuman in January. 
#2 Is it a juvenile and did it lose its way? Generally speaking, fall vagrants are overwhelmingly immatures or more accurately "hatch-year" birds. Note that the "juvenile" plumage of most songbirds is quite short-lived and only remains intact for the first few weeks. Soon after fledging most of the body feathers and some feathers in the wing and coverts are replaced during a preformative molt. This preformative molt will generally be completed before a bird leaves the immediate area where they hatched and before they start migrating. If this catbird hatched in 2022, we can safely assume that it had completed its preformative molt before starting on its path to Oregon. Fledgling/juvenile Gray Catbirds lack the distinctive black cap that they typically show. Once they go through preformative hatch-year birds have a partial black cap that is not as extensive or as dark as what is seen on adults. I just did some eBird gallery surfing to study the differences between adult and immature (first-year) catbirds. What I found is that the black cap is more jet black and extends further back on the crown and onto the nape in adults. On immatures, the cap is darkest on the forehead and gradually becomes lighter towards the hind crown, where it is slaty-gray and only slightly darker than the body plumage. The nuchal area (upper nape) is essentially the same color as the rest of the bird and not black like it would be on an adult. After looking at a number of photos of the Portland bird, it seems conclusively to be a first-winter bird. In a couple of photos it appears to have tell-tale molt limits in the wing and covert feathers, another age indicator.  
Back to the latter half of the original question. A significant majority of fall vagrants are hatch-year birds but are they truly "lost?" I think one can reasonably argue that they are misoriented perhaps, but not truly lost. I say this because there are predictable patterns of occurrence that repeat and have been repeating for generations. The timing of appearance and geographic dispersal patterns have remained consistent. If these birds were truly lost and just aimlessly wandering I would expect a more random pattern of occurrence with far less predictability. Perhaps the best example of predictability I can think of is Eastern Yellow Wagtail. This is a long-distance Asian/Siberian stray that has been found along the West Coast of North America (south of Alaska) on many occasions. Nearly every single occurrence has been along the outer coast (just a couple of inland reports) and the majority of sightings have come not only in September, but generally during the first 15-20 days of September. This may not be the best species to use as example in comparison with the catbird, but it demonstrates that these wayward wagtails are still generally oriented in a single direction and are showing up within an expected temporal window that matches the timing of when they would be headed south on the other side of the Pacific Ocean. Both of these characteristics to their movements suggest a misorientation (not the expected direction but in consistent direction and basically on schedule) rather than lost (no orientation and a more random dispersal pattern with no predictable time table). 

#3 Do they migrate alone? This is another question that is hard to answer. With species that are diurnal as well as nocturnal migrants (shorebirds, ducks, geese etc.) we often see the birds in flocks and often very large flocks. We know that there are energy conservation advantages to their flock structures as individuals take turns breaking the wind at the lead edge of the flock in exchange for the energy conservation that comes from drafting behind the lead birds. Many of these species (particularly shorebirds and geese) are known to make extremely long distance flights, sometimes flying for days at a time non-stop. As a general rule, songbirds don't do this. In most cases they migrate nocturnally and in shorter legs, stopping to rest and feed during the day. If they do flock, it is probably more like what we see with diurnal movements of robins where the birds have no real flock structure or shape, just a loose association of widely-spaced birds. If this catbird is in the minority that are likely misorienting, I would assume that they zigged while all the other catbirds have zagged to follow the more expected migratory route. Catbirds are generally solitary birds that don't seem to ever stage or flock up during winter or migration. I assume that they take flight at dusk like other solitary nocturnal migrant songbirds from wherever they spent the daylight hours. Thus their orientation is likely independent, with no cues being taken from other catbirds. During migration peaks on the east coast and in the midwest it is customary to hear a hodgepodge of nocturnal flight calls from a highly diverse  assortment of migrant songbirds. I don't recall any times when all or most of the call notes I was hearing were from one species (like we get here with Swainson's Thrushes at times). Instead it was a smorgasbord of flight notes from various warblers, thrushes, sparrows, buntings etc. Even along the expected migration routes, I strongly suspect that Gray Catbirds migrate solo. 
#4 What do you think of birdsoftheworld.org etc. Finally an easy one. This is a subscription site, so you have to weigh how much you will use the resource and if it is worth the price. As first a North American Birds Regional Editor and now an eBird Reviewer and Statewide Review Coordinator, I have enjoyed a free subscription to Cornell's Birds of the World website (it used to be Bird of North America) for about 15 years. There is a wealth of great information for someone like me who is interested in subspecies, molt and general distribution. Some of the species accounts are quite good and reasonably up to date, with lots of published peer-reviewed research underpinning the information in the accounts. Some accounts have been revised regularly, by authors who are keen on keeping them as up to date as possible. For other less-intensively studied species, or species for which no author(s) have stepped forward to take ownership, the accounts are little more "boiler plate" and wanting for specifics. In some cases only the original account written roughly twenty years ago exists. In such cases the breeding ecology information may have come from a single study done ages ago. Information about molt sequences and recent taxonomic studies are in some cases extremely sparse or altogether absent. Bottom line, the consistency in the quality of species accounts is not ideal, but most are quite thorough. It is a resource I visit often, particularly when I am looking for information about the identification and distribution of subspecies. It is arguably the best one-stop shopping for descriptions of molt sequences and timing. 
#5 Are range maps just a guide....? At best range maps offer a macro view of each species' distribution...a two-dimensional depiction of geographic distribution without an effective way of displaying seasonality or where within that macro view suitable habitat for that species actually exists. For much of my birding life range maps were as good as it got for showing me where on the North American continent I might find a particular species. I have not critically examined a range map in many years. If I want to look at a map of where a species occurs and doesn't occur and be able to see the individual checklists–complete with dates and geo-referenced locations–for each data point on the map, all I have to do is pull up the eBird map for that species or subspecies. Not a week has passed over the past decade where I haven't looked at an eBird map. Even though range maps continue to be a component in most field guides, I have to wonder how many people really study them the way we used to. I suspect not many. 
To answer your final question...Eastern Screech-Owl doesn't appear to be a good candidate to ever find its way to Oregon. They are essentially non-migratory and have demonstrated no propensity for straying out of range, as in no records anywhere west of the Rockies...not even in California, which gets everything. Being pretty strictly nocturnal and visually quite similar to Western Screech-Owl, I think they only chance of detection would be to hear one calling. These days it is hard enough to find calling Western Screech-Owls, as the invasion of Barred Owl into the PNW has seemingly put a significant dent in their local populations. I've attached an eBird map showing the distribution of Eastern Screech-Owl. The closest population is in west-central Montana, at least 700 miles from Portland.  
Dave Irons Beaverton, OR    

From: Tom Wnuk <twnuk@xxxxxx>
Sent: Thursday, March 9, 2023 11:49 PM
To: David Irons <llsdirons@xxxxxxx>; Wayne Hoffman <whoffman@xxxxxxxx>; Lars Per Norgren <larspernorgren@xxxxxxxxx>
Cc: Oregon Birders OnLine <obol@xxxxxxxxxxxxx>
Subject: Re: [obol] Vagrant Bird Behavior   Great info Dave, Wayne, and Lars….thanks...

It looks like vagrants are truly situational in all cases, you can’t generalize. There’s not really one specific recurring event that exists in nature that we can always point to as the cause for vagrants for well, being vagrants. Sure they might be looking for food and 70 miles as the crow flies isn’t that far.

As I look at the range maps for the Solitaire their year-round area looks to be straight up the Cascades which makes sense why we see them at the lower elevations during the Winter. I first saw one in the Banks Creek in Jan 2008 but only saw it once so assume it was just looking for food, it didn’t stick around.  The recent WashCo Solitaire has been enjoying its Berries even with the presence of its competition, Robin’s. This one exhibits exactly what you’ve been saying, food plentiful, I’ll stick around, food scarce, time to move on and/or create a wider circle of sources.  As Dave pointed out, as it’s time to move to its breeding ground, it well may have moved on.  And as Lars suggested, given the commitment, the Coast range is probably not a bad place to discover more answers to these unknown-never-to-be-truly-answered questions.  I’m not up to that task just yet and as I get older, odds are I won’t be anytime soon.

So, I can wrap my head around the Townsends story, makes sense and has been exhibiting this behavior.

Onto our other subject, the Catbird example.  This one is interesting to me in that the range maps from both Sibley and Cornell (via allaboutbirds.org) show their year round range from Cape Cod all along the east coast down to FLA and along the Gulf Coast with wintering areas south of there in Mexico and Central America. Their breeding grounds are the majority of the rest of the country excluding CA, AZ, NV, & most of NM. Their breeding range also covers most of southern Canada and only the eastern portions of WA & NE corner of OR as Dave pointed out.


….and down the rabbit hole we go…

1. So, why is this Catbird here?

The eBird bar chart shows a 0.5% frequency in most of June with the rest of the year lower and <0.1% in parts of Feb & Mar and non-existent in April.


Did it start to migrate south and got distracted by good food sources along the way or was it dodging predators and found itself here (unlikely). As Dave pointed out, unlikely it came from the breeding area in central WA; so, where did it come from, Southern Canada and needed to stop and refuel.  That makes sense to me and since it found a good spot, decided to stick around.

2. Can we say if it’s a first year Juvenile and lost its way? 

3. Do they typically migrate alone? 
Is this true for all Songbirds or is this one an outlier traveling alone.

If a juvenile, it seems to be very well schooled in maintaining good cover as the Cooper’s hawk hasn’t dined on it yet but then it probably has more easily attained menu items.

Should it not have migrated south well before January when it was first seen even though we don’t really know when it arrived. Based on what I could find, they tend to begin their southern migration sometime after September.

I’m guessing that if I want to really understand these specific behavior details I can either pick one and study it through both reading material as well as watching live in-person in the wild as each species is unique.

4. What do folks think of the https://birdsoftheworld.org/ <https://birdsoftheworld.org/bow/home> as a resource?

It’s not something I would probably want to subscribe to year/year but given the annual cost is 1/2 the monthly rate, a 1-year subscription assuming I use it, could be very educational unless you all believe it really won’t answer these questions but will provide more insight than what I may have today.

Dave, how would you position the Red-necked Grebe that’s been at Hagg Lake for the past 2 months? 
Blown off-course and has an adequate food supply, not in any hurry to return to their breeding grounds. If I only looked at the range maps, they shouldn’t be here in Oregon but eBird tells a different story. The range map shows it’s Wintering grounds to be the western coast of Canada/Alaska and southern coast of Alaska.

5. Are the Range maps just a guide and should be taken as a coarse representation of what’s typical meaning highly unlikely to ever see an Eastern Screech Owl in Oregon?

Note, I numbered the questions as I want to make it easier to reference and also be readable in plain-text for those Digest users.  If I was using rich-text I could have bolded the questions or used different colors, etc..  As a former Digest user, my switch to receiving each Post directly has been beneficial in many ways.

Thanks all.
-tom



> On Mar 8, 2023, at 10:25 PM, David Irons <LLSDIRONS@xxxxxxx> wrote:
>
> Tom,
>
> I will try to work through the questions below in order. One of the great things about birding is that as you find answers to one question, others invariably follow...a never-ending maze of rabbit holes to find your brain wandering into.
>
> I'll start with the Gray Catbird wintering in SW Portland. This species has an expansive range north to south and east to west. We generally think of catbirds as "eastern" birds but they breed in some numbers at Trout Lake, Washington, which is only about 70 air miles from Portland and there are lots of breeding outposts farther north and east in Washington and across the NE quadrant of Oregon. Their range extends well north into Alberta and Saskatchewan. In trying to guesstimate their migration timing I looked at some eBird bar charts. The statewide bar chart for Illinois shows a spike in catbird numbers about the third and fourth weeks of April. They arrive about mid-May in Washington, so it seems likely that the SW Portland bird could linger here at least into early April, if not later. It is impossible to know where the Washington County catbird came from, or when it arrived at the site. It is not safe to assume that it came from one of the proximal nesting sites in Washington or even NE Oregon. It is likely to have come from a breeding population generally north of Oregon's latitude, but even that isn't a certainty. I pulled up the eBird map of Gray Catbird sightings from June and July over the past five nesting seasons and found numerous reports of multiple birds for these eastern Oregon counties: Baker, Grant, Umatilla, Union and Wallowa. I think it is safe to assume catbirds are at least low density breeders in all of these counties. Over the past two decades catbirds have been found during nearly every summer somewhere in Klamath and Deschutes Counties, leading to speculation that they probably breed at least sporadically in these counties. Catbirds are reasonably hardy, thus a few winter at higher latitudes so long as they have access to food. The Washington County bird has a suet feeder and lots of berries along the hedge bordering the yard to feast on, so there is no reason for it to leave any time soon. I don't know if anyone has seen it go to the meal worm feeder. Like most of the mimids, catbirds tend to stay in dense cover most of the time except when they are actively feeding. Given their retiring habits, no matter how this bird remains it is not like to start sitting out in the open. That's not what catbirds do.   
>
> The Koll Center Wetlands Townsend's Solitaire is likely to have a completely different timeline. Townsend's Solitaires are more hardy than catbirds and they routinely winter at this latitude and even farther north. Their winter diets consists mostly of hard waxy berries. When the Koll bird first showed up it was found day after day in the same tree near the southeast corner of the main lake. There were lots of berries on the tree when it first arrived. That same tree has not had a berry on it since back in January, thus the solitaire moved across the lake over by the tennis courts, where it found another source of berries. The last time I was over there, I couldn't find any trees or bushes with berries and no solitaire either, so it is likely that the solitaire moved again to find food, or perhaps it has migrated. We are now into the time of year when Townsend's Solitaires start migrating. Along with American Robins, Say's Phoebes, swallows and of course Rufous Hummingbirds, Townsend's Solitaires are one of our earlier spring migrants, with influxes becoming apparent in some areas by late February. In most years, there is a flurry of Townsend's Solitaire reports in the westside lowlands and foothills usually starting in March and lasting into early April. They have not all been reviewed yet, but looking at the statewide eBird review queue the other day I noticed several new westside solitaire reports from just the past week. Solitaires winter in the streamside lowlands of central and eastern Oregon in places where there are sources of berries, particularly western junipers. When they show up west of the Cascades in early spring they are often found around big patches of berry-laden English ivy. When feeding, solitaires tend to sit pretty still as they gorge themselves on berries, only moving occasionally and deliberately, or with a brief flutter to bring more berries into reach. When not feeding, they often sit quite still for extended periods, sometimes perched out in the open but more often perched slightly hidden in the mid-canopy.
>
> You mention birds being "blown off course." One of the common misperceptions is that birds found out of place end up where they do due to weather. While this is true for some groups of species, most notably seabirds that get caught up in hurricanes and tropical cyclones, it is likely that only a minority of the vagrant songbirds we see in the West are ending up here because of a wind event or a storm of some sort. Many decades ago Dr. David DeSante, who passed away just last fall, did a bunch of studies with mist-netted vagrant songbirds captured at Point Reyes and the Farallon Islands along the central California coast. What he found was that these birds were to some degree hard-wired to migrate on a heading that was essentially a "mirror-image" of where they should have been headed. Even after being captured right along the immediate coast and on the Farallons 18 miles offshore, the birds preferentially wanted to head in a direction that would carry them out to sea to almost certain demise. Many species of fall vagrant eastern warblers show up in some numbers each and every year within predictable date ranges and in the same "traps." They show up regardless of what the weather pattern might have been across the mid-continent when they start migrating. Occasionally, there are anomlous weather patterns that make for spectacular vagrant flights, but weather is not necessarily a primary factor in their wanderings. It should be noted that local weather such as cloud cover and fog along with wind direction can make a difference in whether it is a good day or poor day for finding vagrants along the California coast, but the birds were already headed there for reasons other than weather.
>
> You mention electronic tracking. I don't know if much study has been done on the impacts of birds being fitted with lightweight transmitters, but the Motus project has great potential to provide answers that have long eluded us. These tiny transmitters ping off of a network of tracking towers going up in the Americas and perhaps all around the globe eventually. The Canadians are way ahead of us in terms of both putting up tracking towers and radio-tagging birds, in part because the Canadian government is investing heavily in this effort. There are only a few widely scattered towers across the western U.S., not nearly enough of a network to reveal the exact migration routes of individual birds, but hopefully that will change over the next decade or so. If you have the money and a good site to put up a tower you can buy one for yourself and become a data contributor. The cost of equipment ranges from $3000-10,000. (see link below for answers to common questions about the Motus project). These tracking towers can pick up migrating birds at a distance of up to 15 miles (sometimes more depending on terrain). It's like being passed from one cell tower to the next if the towers are located close enough together. With a dense network of tracking towers we can determine where birds stop to rest, how often they stop, and how long the breaks last. We can answer all sorts of questions with this technology, such as how much do birds of various types move around during the winter season? How many miles do they travel each day when migrating? Where are the pinch points along major migration routes where masses of birds pass through as they move north or south? 
>
> https://motus.org/faq/ 
> I hope this answers some of your questions and more importantly spawns more.
>
> Dave Irons
> Beaverton, OR From: Tom Wnuk <twnuk@xxxxxx>
> Sent: Thursday, March 9, 2023 2:39 AM
> To: David Irons <llsdirons@xxxxxxx>
> Cc: Oregon Birders OnLine <obol@xxxxxxxxxxxxx>
> Subject: Re: [obol] Re: Vagrant Bird Behavior
>  Thanks Dave.  I changed the subject line in case this becomes a longer discussion and we can separate it from my original Post.
>
> Now I have more questions. What you describe makes perfect sense but leads me to wonder about the following.
>
> Assume the vagrant is staying over the Winter (e.g. Gray Catbird, Townsends Solitaire, both WashCo )
>
> The above two may be different but good examples as the Catbird (first seen 1/21/23 - last seen today, 3/8/23) seems to be overstaying the Winter; whereas, the Solitaire (first seen 11/10/22 - last seen 2/25/23) may have found a new home or ???
>
> 1. Both seem to be doing well when it comes to staying out of sight although one has been more visible lately and the other has not been seen for over 11 days. Can I assume once they begin to feel safe, they become more visible at the risk of becoming dinner for a predator or are starving and will do whatever is necessary? 
> e.g. the Coopers Hawk that sits overlooking the Catbird location has a lot to pick from due to the backyard feeders
>
> 2. Since it has been well over a week since the Solitaire has been seen and based on your explanation, would you surmise it became prey or was it time for it to head back to where it once came?  I know
>
> 3. Assuming the Catbird traveled farther than the Solitaire and it becomes time to travel back to its breeding grounds, how does it know how far off-course it is and how much time is needed to get back there assuming it actually knows how to get back.  I guess another way to ask this is how do vagrants find their way back “home” if they’ve been blown off-course by 100’s maybe 1000’s of miles?
>
> 4. I assume we can never know what really occurs unless we electronically track them which means we have altered their physical being.  Do we have evidence based data that we know conclusively that these devices don’t impact their behavior?
>
>
> I will probably have more questions but this is my initial response and realize there’s no one answer that fits all scenarios as each is unique.
>
>
> thanks
> -tom
>
>
> > On Mar 8, 2023, at 4:46 PM, David Irons <llsdirons@xxxxxxx> wrote:
> >
> > Tom,
> >
> > I will take a shot at the last part of your question, not that this is likely to be a complete answer. You asked:
> >
> > An example of an edge case would be why do some rarities stick around all winter while some just pass through in a 24-hour period.  I understand the basics of why but am wondering if there’s something more or is it simply food and breeding. Maybe that’s what I’m looking for, the nuances / edge cases.
> >
> > There are a number of factors to consider when thinking about if or why a vagrant bird will overwinter. The first question to answer centers on, is the bird actively migrating? Many species are still actively on the move southbound in December and for other species the northbound migration may start before what we consider to be the spring migration window. If a bird first appears at the margins of the winter season it may be on the move. If the first sighting of a rarity occurs during the early December window the bird may not have settled into a site where all of its winter needs will be met, thus it is a one-day wonder. Another question to ponder is, what is the latitude where this species normally winters? In other words, should I expect it to stop at my latitude? This is often demonstrated by strays from Asia and Europe. When they end up on the wrong side of the ocean they tend to stop and winter at a latitude similar to the one where they normally winter. Good examples of this are some of the Siberian strays that have wintered in Baja.
> >
> > As you noted in framing your question, food availability plays a big role in where birds winter, along with supplies of fresh water, suitable cover/roost sites, and safety from predators. Sometimes a bird will show up in early winter and be reliable at a site for a period of weeks and then suddenly it disappears in mid-winter. Odds are that it did not decide to move on in the middle of the season. It's more likely that the bird starved, froze, or fell victim to a predator. Once a songbird finds a site that checks all of the boxes above (reliable food, water, cover, safety from predation) they generally seem to settle in for the season and can be reliably refound at a site until the normal time for their spring migration arrives.
> >
> > Of course there are all sorts of variables that add nuance and mystery to our understanding of why birds do what they do. The Sibley book several of us recommended may help in answering basic questions about bird behavior that to a degree translate to what a particular speices might do when it strays off course. As Rich suggests, the "Rare Birds of North America" is probably a better reference if you trying to better understand the behaviors of wayward birds and what factors influence whether or not they stick around. Someday I hope to have better answers to these questions, perhaps resulting in a better success rate in finding these vagrants. I'm sure I am not alone in that regard.
> >
> > Dave Irons
> > Beaverton, OR   
> >
> >
> >
> > From: obol-bounce@xxxxxxxxxxxxx <obol-bounce@xxxxxxxxxxxxx> on behalf of Tom Wnuk <dmarc-noreply@xxxxxxxxxxxxx>
> > Sent: Wednesday, March 8, 2023 2:36 AM
> > To: Oregon Birders OnLine <obol@xxxxxxxxxxxxx>
> > Cc: Tom Wnuk <twnuk@xxxxxx>
> > Subject: [obol] Bird Behavior Recommendations   Anyone have recommendations for an in-depth look at Bird Behavior across the Bird Families?
> >
> > I had taken the Cornell Ornithology home study course in the late 90’s but between multiple moves seem to have lost that material and now it’s online and has been updated; so, I’d have to purchase again. It also doesn’t go deep into behavior.
> >
> > I’m looking for a more in-depth look not the basic info.  Birds of the World has a good overview but still doesn’t go deep enough. 
> >
> > An example of an edge case would be why do some rarities stick around all winter while some just pass through in a 24-hour period.  I understand the basics of why but am wondering if there’s something more or is it simply food and breeding. Maybe that’s what I’m looking for, the nuances / edge cases.
> >
> > There are many resources on Amazon for instance but they all seem to be general info.
> >
> >
> > thanks
> > -tom *******
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