Wednesday, February 14, 2018

Greater Scaup: An eBird problem child

[Click on images to see larger versions.
Immature male Greater Scaup, Cape May Pt., Cape May Co., NJ; 7 January 2012. Photograph by Tony Leukering.]

Greater Scaup is of regular occurrence in our two-state region, but is both over- and under-reported, due to the extreme difficulty that many birders -- even skilled ones -- have at identifying scaup.  Leukering has treated this subject in some detail elsewhere (Leukering 2011).  We strongly recommend reading that paper first, but we know you won't, so this essay is meant to point out a few factors in scaup identification that are over-looked or ignored by -- or unknown to -- many birders.

We start with some bulleted cautions:

  • If the scaup that you are ogling is foraging; beware!  Head shape is not a useful differentiating feature of foraging scaup.
  • If the scaup that you are ogling has water drops on its back and/or elsewhere; beware!  That bird has recently been foraging; see previous caution.
  • If the scaup that you are ogling does not have bright yellow eyes; beware!  Dull eye color is a sign of immaturity, and head shape in scaup with juvenile head feathering is not a useful differentiating feature.
  • If the scaup that you are ogling is a male that lacks complete adult-like plumage, particularly after December; beware!  Males lacking complete adult-like plumage after December are probably immatures; see previous caution.
  • If the scaup that you are ogling is brown; beware!  The timing of the molt out of juvenile plumage is quite variable across individuals of both species, such that immature males still with juvenile head feathering can be found very deep into winter.  Additionally, eye color may change well ahead of plumage change, such that even scaup with yellow eyes may still hold juvenile head plumage; see previous caution.
  • If the scaup that you are ogling is brown and large and has a slight peak in front of the eye; thin-but-distinct eye rings; thin, pale post-ocular line; and looks like this; beware!  The bird that you are ogling is a female Redhead.
  • If the scaup that you are ogling has an apparently green head; beware!  The iridescent plumage of male scaup is not, WE REPEAT, NOT, a reliable differentiating feature of scaup -- or of any other similarly plumaged species.  Note the head color of these males: 

               November, California

               January, Florida

               January, Colorado [the best of the lot]

Scaup ID has always been difficult, with, perhaps, the majority of birders not being able to consistently ID them correctly.  Even skilled birders have trouble with this duo, so do not be afraid to use the "Greater/Lesser Scaup" entry in eBird.  In fact, we will make it more plain:  Use the "Greater/Lesser Scaup" option unless you are certain of the ID of the scaup (singular or plural) you are ogling.

Okay, one more caution, and then we'll get to the meat of this essay.  Finally!


  • If the scaup that you have ogled is represented in your photos/eBird checklist by a single picture; beware!  Head shape is changeable and ephemeral, and as with identification features, the more of them you have, the better.  The more photos, the more likely that you will have captured the "true" head shape.

  • One of the problems that birders create for themselves concerning scaup ID is not knowing the difference in sizes of various duck species.  For whatever reason or reasons, many or most birders seem to think that diving ducks are large, particularly relative to dabbling ducks.  However, the reverse is true.  Paying attention to neighboring ducks when ogling a scaup and determining the scaup's comparative size is very helpful.  If that scaup is among other "bay ducks" (genus Aythya), size can be quite helpful, as:

    Canvasback > Redhead > Greater Scaup > Ring-necked Duck ≥ Lesser Scaup.

    If that scaup is among dabbling ducks, then:

    Mallard > Northern Pintail > Gadwall ≥ American Wigeon > Northern Shoveler > 
    Greater Scaup > Lesser Scaup ≥ Cinnamon Teal > Blue-winged Teal > Green-winged Teal

    Combining all of these species results in:

    Mallard > Northern Pintail > Gadwall ≥ American Wigeon > Northern Shoveler > Canvasback > Redhead > Greater Scaup > Ring-necked Duck ≥ Lesser Scaup ≥ Cinnamon Teal ≥ Blue-winged Teal > Green-winged Teal

    Of course, the above comparisons are over-simplifications, as I created them from the "average" size values presented in Sibley (2014) [Yes, actually reading the field guides can prove quite useful in bird ID] and the wing-chord values in Pyle (2008).  Unfortunately, there is variation in size in all species, with males averaging larger than females and, at times, adults being larger (at least, bulkier) than immatures.  So, again, determining your mystery scaup's age and, particularly, sex can be critical to slapping the correct ID on the bird, and, below, we present a great example.

    The recent incredible increases in both the number of birders and in the ease with which information about bird occurrences can be shared has exacerbated the problem of mis-identification of scaup.  Additionally, one of those sharing venues -- eBird -- has particularly exacerbated the problem, as anyone can report bird occurrence to eBird, even when the identifications that result in those bird-occurrence data are incorrect.  Thus, the fact that a single birder incorrectly reports a Greater Scaup from a location can create a situation of circular logic about that occurrence, with many other observers visiting that location and also incorrectly reporting that "Greater Scaup."  These sorts of things then take on a life of their own, as few observers then critically examine the bird in question, because "the bird has been reported by others," so one of these scaup must be the Greater.

    This essay is the direct result of one of those situations. Someone (I know not who, and it does not matter) reported a male Greater Scaup at Belmar Park in Jefferson Co., CO, in January.  Others followed, some reporting a Greater Scaup; still more others followed.  Kathy Mihm Dunning, Scott Somershoe, and Tony Leukering, due to eBird-review duties, had seen a number of photos from the location of the purported Greater Scaup, and were sure that the various reports were in error, as none of the photos embedded in eBird checklists provided definitive proof of ID.  In fact, many photos were obviously of Lesser Scaup; some were less-obviously of Lesser Scaup.

    Kathy and Tony visited Belmar Park on 3 February to attempt to solve the problem.  As can be seen in the resultant checklist, they found ten individual scaup.  The number of Lesser Scaup reported on the other 41 checklists that reported scaup from Belmar Park in January and early February 2018 ranged from one to ten.  Greater Scaup were noted on 14 of those checklists, with all but one checklist reporting a single bird.  Thus, it seems unlikely that the "Greater Scaup" in question was/were not present for their visit.  In fact, some of the photos of the purported Greater Scaup were more-than-good enough for us to determine that we saw the same individual birds.  Unfortunately, those birds were Lesser Scaup.  BUT, there was a very interesting brown scaup.  In fact, it was one of the birds depicted in the single checklist that reported brown Greater Scaup.

    When endeavoring to identify a scaup, as with identifying most birds, determining the bird's age and sex are quite helpful when hoping to arrive at a correct ID.  Conversely, if one is not hoping to arrive at a correct ID, then age and sex don't play any useful part.  The primary reason that ageing scaup is critical for species identification is that the head shape of juvenile scaup, particularly that of Lesser, is somewhat to quite different from that of adults.  Yes, the heads of juvenile Lesser Scaup are often fairly rounded.  Here are some examples of immature Lesser Scaup in fall:

    November, El Salvador

    September, Idaho

    September, Idaho [we particularly like the great variety of head shapes depicted in this photo]

    October, Ontario

    Of the Lesser Scaup at Belmar Park on 3 February, there was just a single male wearing complete (or nearly so) adult-like plumage; it is depicted in Figs. 1-2. All other male scaup present were obvious immatures (such as the second bird in Figs. 1-2).


    Figures 1 and 2. Adult male (right) and immature male Lesser Scaup. Note the peaked crowns of both birds, but that the immature's crown is less-peaked. Also note the immature's mix of juvenile and adult-like plumage. Belmar Park, Jefferson Co., CO; 3 February 2018. Photographs by Tony Leukering.

    The only scaup present that caused a slight increase in heartbeat rate was the bird presented in Figs. 3-6 and which provides the aforementioned great example of the usefulness of size comparison when identifying ducks.

    Figure 3. The interesting brown scaup. Note the disheveled plumage on the crown that makes the bird look like it's having a bad-hair day; that plumage is almost certainly juvenile crown plumage, and worn juvenile crown plumage, at that. Also note the handful of grayish feathers present on the sides, which present as whitish streaks. Also note the oddly orange color to the plumage encircling the bill. We do not know what that color means, but it makes for a distinctive scaup. The brown eyes indicate that this bird is an immature. The bits of gray side plumage indicate that this is a male, not, as one might think, a female. Note that it appears quite a bit smaller than the male Northern Shoveler behind it. Finally, note that that male Northern Shoveler's head is purply-blue, not green. Again, the color of iridescent plumage is highly unreliable as an identification feature. Belmar Park, Jefferson Co., CO; 3 February 2018. Photograph by Kathy Mihm Dunning.


    Figure 4. The interesting brown scaup. Note the bird's apparently blocky head, non-peaked crown, and steep forehead. Part of that appearance is due to ephemeral posture, part due to retained juvenile head plumage. Since by this time that juvenal head plumage has been adorning the bird for, perhaps, 7-8 months, it is getting quite worn. That means that the feathers are becoming shorter, which may account for a few of the apparent Greater-like head features presented in this photo. This photo is also highly relevant to the above caution about using a single photo to describe your scaup. Belmar Park, Jefferson Co., CO; 3 February 2018. Photograph by Kathy Mihm Dunning.


    Figure 5. The interesting brown scaup. Note the bird's relatively narrow head and shallow angle created by jowls that do not bulge much (compare with birds on back cover comparison in this essay). Belmar Park, Jefferson Co., CO; 3 February 2018. Photograph by Kathy Mihm Dunning.



    Figure 6. The interesting brown scaup. Note that the scaup looks noticeably smaller than even a female Northern Shoveler. Belmar Park, Jefferson Co., CO; 3 February 2018. Photograph by Kathy Mihm Dunning.

    If you've slogged all the way through the essay: Thanks!  If you've skipped ahead, the solution set to the murder is:  Colonel Mustard, in the kitchen, with the wrench.

    Literature Cited

    Leukering, T. 2011. Greater and Lesser Scaup: Beyond crown shape. Colorado Birds 45:75-78.

    Pyle, P. 2008. Identification Guide to North American Birds, part II. Slate Creek Press, Bolinas, CA.

    Sibley, D. A. 2014. The Sibley Guide to Birds, 2nd ed. Alfred A. Knopf, New York.


    Tony Leukering, Steve Mlodinow, Kathy Mihm Dunning, and Scott Somershoe (half of the Colorado eBird review team)


    Friday, January 26, 2018

    The "Show Rarities" box

    As an eBird reviewer, I am continually surprised how few eBirders know about the "Show Rarities" box.  Except for those few eBirders that look only at the birds at their feeders and who never host (knowingly or otherwise) a local rarity at those feeders, all eBirders will eventually run across something that is considered locally rare.  That is, the entry gets flagged by the relevant eBird filter.  This is particularly true for those folks that don't eBird regularly, but occasionally chase interesting stakeouts, such as this year's crop of Snowy Owls.

    The result of this ignorance of a basic part of eBird's infrastructure is that such observers usually wind up putting an entry for the chased Snowy Owl, or Red-breasted Sapsucker, or Brambling into one or another of the various "spuh" categories.  In fact, this winter's Snowy Owl movement is really obvious anytime that I go to look at the photos entered into the "owl sp." entry, because the observer did not know about the "Show Rarities" box.  Since the eBird program is very light on instruction as to how to use eBird and a lot of people hate "reading the manual," it is left to reviewers to explain to observers (or, in many cases, not) how to get those various rarities into the species entry, rather than letting them languish in an unidentified category (which serves almost no one well).

    To find the "Show Rarities" box, one must be in the process of submitting a checklist directly via the Internet (that is, NOT via the eBird app) OR be editing an existing checklist (which one cannot do from the eBird app; at least, not yet).  The "Show Rarities" box is on the right side of the checklist-view page, as indicated here (click on images to see larger versions).  However, to get to the checklist-view page, you will have had to click on the "Edit Species List" button immediately after you opened the relevant checklist (Fig. 1).

    Figure 1. This is the page that you see when you open an existing checklist (that is, one that you are not currently entering originally). The arrow points out the button on which to click to get to the checklist-view page (Fig. 2).



    Figure 2. The "Show Rarities" box is shown by the arrow.

    If the entry for which you are looking is not presented in the checklist, look at that check box in front of "Show Rarities" to make sure that it is checked (it is not checked in the above graphic).  If that box is unchecked, simply click on the box and the check-mark will be added.

    However, if that check-box is already clicked and the entry for which you search is still not present, look above the "Show Rarities" box for the "Add species" feature.  Clicking on "Add Species" will open a dialog box that will allow you to enter the entry for which you search, whether that is "Picoides sp.," "Wandering Albatross,", or, as in Fig. 3, "Great Gray Owl."



    Figure 3. Once the "Add species" dialog box opens, simply start typing in the name of the entry.

    In the example provided in Fig. 3, I have started typing "Great Gray Owl" and have not gotten to the owl part, but the option that I want is the first one on the list. Simply highlight that option (here, it is in blue) and click on it to move that option into the dialog box.  Once that ation is completed, eBird will give you the screen presented in Fig. 4.


    Figure 4. After filling in the dialog box in the previous step, this screen is the result.

    Notice that eBird has filled in the number box, assuming that an observation that requires adding a species to the checklists -- that is, one that is not even on the relevant filter, would be rare enough that the likelihood of seeing more than one is low.  If, however, one does wish to report more than one, simply highlight the number (or put the cursor to the right of the number and press the 'backspace' key) and type in the number that you wish to report.  Then, because this entry is considered locally rare, you will need to provide details in the "Details" box.  Of course, if you're simply trying to add an unidentified category (one of the "... sp." entries, called "spuhs" by eBird folks), then you'll need to just add a short note in the "Details" box as to why you're using it, and that that entry might need to be added to the relevant filter.  Once you have completed those steps, simply click on the big, green "Save" button, and you can continue on your merry way.











    Wednesday, January 24, 2018

    The new "Change Species" button

    For most of eBird's history, if one made a mistake and entered data in the wrong entry, to fix it, one needed to put all of the relevant information (number of individuals and any data on age/sex, etc.) into the intended entry and then delete the mistaken entry.  This was a bit annoying, but particularly so if one had uploaded photos into that entry.  One might have lost track of those photos, but even if one hadn't, just finding them and re-uploading was another minor pain.

    Late in 2017, eBird introduced a great new checklist-editing tool: the "Change Species" button.  This new button allows quick-and-easy transfer of data and embedded media from one entry to another, as long as there are not already data in the target species entry.  This post is meant as a how-to essay on the mechanics of using the "Change Species" button.

    After opening the checklist in question, click on the "Edit Species List" button (click on images to see larger versions):


    After clicking on that button, eBird will then provide you access to the various entries in the bird list:


    In the above screen grab, we can see that I have entered the number of birds and a photo into the "longspur sp." entry, an entry that I had used as a place-holder until I could go through my photos and figure out a reasonable ratio of the longspur species present (Lapland and McCown's).  So, now that I've done that, I can move the data AND the photo into the McCown's Longspur entry very easily by clicking on the "Change Species" button visible to the right of the species/category name.  [If you want to move only the media, click on the "Only my media" radial button.]  Once I click that button, I see this:


    Since I want to move the number of individuals AND any other data or photos, I make sure that the "Entire observation" radial button is highlighted (rather than the "Only my media" radial button).  Then I start typing into the blue ovaled box under "Change species identification to" the name of the species into which entry I wish to move the information.  Once I start typing in the name, eBird starts giving me options that match the set of letters typed to that point.  Because there is only one bird species in the world named after Mr. McCown, once I've gotten that far, that species is the only one offered:


    However, for other species, you may have a couple to many options for species, depending upon how far into the name you've typed.  You can scroll down the list and highlight the entry that you want and click on it, which will then show in that ovaled box:


    Then, make sure that everything presented is correct and, if so, click on the green "Change" button, which will give you this screen:


    Then, go through the checklist and make sure that everything is copasetic (or hunky-dory or the way that you want it) and click on the big, green "Save" button.

    You're done.  The process actually takes much less time than does reading this blog post.

    Wednesday, August 9, 2017

    eBird basics: The species comments box

    For every entry that one makes in eBird, one has the option to provide comments.  You can put whatever you want in the comment section, but for flagged reports, details that describe the bird and eliminate other species, or how you documented a high count, are needed. Why should I add such information? This provides the information up front and saves the local reviewer time, effort, and, possibly, annoyance. Observers may also come to pay closer attention to details on uncommon and rare species, subsequently increasing observer skills, and providing valuable information that's archived for people 10 or 20+ years down the road.

    Each species, subspecies, and undetermined entry has a comments box that is accessed by clicking on the "Add Details" button to the right of the species (or other entry) name (Fig. 1).

    Figure 1. The "Add Details" button that leads to the species-comments box (see below).

    Clicking on that button leads to opening what eBird calls the "Details" box (Fig. 2).  It is intended as a place to put comments on the species (etc.) that one is reporting.

    Figure 2. The opened species-comment box. Other useful features shown in this figure include the "Show Rarities" box (check it if the species you wish to report is not on the checklist) and the "Add species" link if that species still does not show after checking the "Show Rarities" box.
    One can add most anything to this box that one wishes; it sees a lot of use.  Such comments, are varied and "include things like "Life bird #263;" "bird was visiting the right-most feeder in the back yard;" "I would not have seen it if it weren't for the ball game being pre-empted;" or "in a tree."

    As I wrote, one can put nearly whatever one wishes in that box.  What eBird reviewers wish, however, is that more eBirders would use that box to provide details on how that bird or those birds were identified or at how the reported number was arrived?  For species that the local filter considers rare, provide details on features that were noted that enable identification, with the amount of detail proportional to the level of rarity.  Perhaps more importantly, provide notes on what features were noted that rule out other, similar-appearing species.  [See an article about just such.]  For entries that are flagged due to a high number, a simple comment on how the number was derived is what we want:  "counted 1x1," "counted by 10s," or "estimate" usually suffice.

    For minor rarities or slightly out-of-season birds, a sentence or sentence fragment listing the aspects of the bird seen/heard may be all that is needed (e.g., "red, crested bird with black mask," "large bird of prey... white head and tail, dark brown body," or "long, slow, wolf whistle coming from above ground").  Indeed, for most entries that the relevant eBird filter flags, causing you to have to confirm your entry, such examples are often all that the local reviewer would need to allow the report into the public database.  For rarer events or trickier IDs, more details on the bird or birds' identification would be needed (Fig. 3).  If one has a photo or photos and if one is entering the data via the eBird app, then providing the comment "photo" or "I have photos" is fine as a place-holder, but not as a final comment.  If one has photos, please upload them using the "Media" tab (Fig 2).


    Figure 3. Reviewer-useful comments on a species that is only slightly rare, but is a somewhat-tricky subspecies identification.
    For even rarer occurrences, be prepared to provide quite a lot of information in this box, preferably with a photo or photos and/or audio files added to the species entry via the "Media" tab (Fig 2; also see this Eastern Meadowlark example).

    Particularly if one is reporting a checklist using the eBird app, putting the comment in that you have a photo or photos is fine, as long as one soon thereafter uploads the photo into the checklist.

    So, why do this?  The easiest answer to that question is that it will save time in the long run.  Any flagged entry is liable to be queried by the local reviewer.  Why wait?  Why have to go through the query-response cycle (or the query-response-query-response, etc. cycle)?  Providing the information up front saves that local reviewer time, effort, and, possibly, annoyance.  It is a good thing to do in the care and feeding of your local eBird reviewer.

    Finally, some observers question why a particular report is flagged and use the comments box to post it.  This is fine.  However, some of us have spent a LOT of time fine-tuning the filters that govern what is flagged and where, and being rude about that query is not at all helpful.  Instead of terse comments such as "not rare," something like "Could you explain why this entry is flagged?"  Except in a few filters in Colorado and Wyoming that have not seen a lot of work in recent years, there is good rationale behind the various filter limits.  We suggest that you check previous posts on this blog, as your question may have been answered there.

    Tony Leukering, Scott Somershoe, Steve Mlodinow, and Kathy Mihm Dunning


    Friday, March 18, 2016

    eBird checklists and miles traveled

    One of the tasks that eBird reviewers find difficult is dealing with checklists that involve long, traveling counts.  Such checklists often stand out because they tend to rack up relatively large numbers of individual species, thus tickling the relevant filter and getting particular species entries flagged.  However, a large percentage of such checklists have no flags, thus do not see review until and unless a reviewer goes searching for anomalous eBird locations of habitat-restricted species, such as, say, White-tailed Ptarmigan.  In fact, these habitat- and range-restricted species are the primary argument for having checklists with as precise a location as possible, else the resultant eBird maps show occurrence in areas or habitats in which the species does not occur.

    Unfortunately, the most comprehensive treatment of the subject is not that comprehensive and does not provide any hard-and-fast ground rules.  Granted, hard-and-fast rules when dealing with biology are nearly impossible, but eBird does care, and care strongly, about checklist locations.  In fact, I'm sure that if it were possible, eBird would prefer a checklist and associated precise location for every individual bird.  Of course, that is not going to happen, at least, not anytime soon.  However impossible the every-bird-is-its-own-checklist pipe dream might be, there are definite and very strong advantages to eBird of having checklists cover as little distance as we can get from eBirders.

    The best guidance that I have found in the eBird 'Help' tab is the "Traveling Counts" section of a general-purpose essay on making checklists more useful:


    Traveling counts have proven to be the most effective type of observation for modeling bird populations at large scales.  By doing these counts, birders often detect a good proportion of the birds in a given habitat.  It is critical, however, that your traveling counts not be too long.  Our analysts are able to effectively use traveling counts that are ≤5 miles [emphasis added].  Most birding that is conducted on foot easily falls within this window, but traveling counts by car can often be longer.  Please consider breaking up your long traveling counts into shorter-distance ones. It's best if these shorter counts are in a relatively consistent habitat, or do not pass through habitats that are too different. For example, a logical point to break a longer route into segments would be a transition between forest and farmland, as the birds found in these two habitat types are vastly different. Doing so would make information associated with each location — such as vegetation information from satellite images — more informative.  Plot your location at the center of the area traveled, not at the start point or end point.  It's okay to stop and spend time searching flocks of birds more thoroughly on traveling counts, as we are not assuming that you are traveling at a constant speed.  You're birding after all!
    I here note that eBird Central has repeatedly stressed that this "five-mile limit" should NOT be considered cause, in and of itself, for checklist invalidation, that the limit is simply one that is very useful in particular types of analyses, such as the STEM maps of migration of individual species.  Checklists covering trips of a reasonable longer distance are certainly permitted in eBird and most such provide perfectly valid and useful data.  The problem that eBird reviewers face is where to draw the line on "reasonable."

    Certainly, any eBirder should recognize that a checklist covering 650 miles on I-80 and crossing a state boundary (possibly, multiple state boundaries) and who knows now many dozens of county boundaries, does not provide data useful to anyone other than the observer.  In fact, such would provide misleading information, as almost no matter where such a checklist were plotted, the list of birds could well include species not regularly found at or near the plotted location.  But where lies the "reasonable" cutoff between 650 miles and five miles?  Unfortunately, this illusory line is dependent upon where you are and what sort of areas are covered by the checklist.

    In much of the flatlands of Wyoming and Colorado, a checklist covering 15 miles, even 20 miles, might include just one or two habitats (e. g., native grassland and winter-wheat fields) that share a large proportion of bird species present in the area, and thus provide reasonable eBird data.  However, in places like southwestern Huerfano County, Colorado, traveling on the road from Highway 12 toward Trinchera Peak -- the straight-line distance of which is just over 4 miles (though the road distance is a fair bit longer) -- one's elevation changes from roughly 9250 feet to over 12,100 feet.  This road takes one from about the upper limit of elevational range of species like Pygmy Nuthatch and Black-headed Grosbeak and the lower elevational limit of Gray Jay and Pine Grosbeak to the above-timberline habitat of White-tailed Ptarmigan and American Pipit.  Thus, any checklist covering the whole road will, perforce, require plotting some of the birds encountered in habitat different from that in which they typically occur.

    The above brings us back to the aforementioned eBird guideline about traveling distance and its emphasis on habitat.  Though not stated precisely in the guideline, eBird is very much interested in checklist locations being fairly specific to the habitats of the species included on the checklist.  Thus, in areas of the two-state region in which many habitats meet and mingle -- particularly obviously differing habitats, such as grassland and woodland or conifer forest and alpine tundra, the more precisely that locations are plotted and the shorter distances that are covered by individual checklists the better.  With the eBird application (app) for smart phones (about which, please read the best-practices essay), this becomes quite easy to manage.  Granted, cell coverage in much of the two states leaves much to be desired, but there is a simple work-around when planning a trip to an area of poor cell coverage.  One can modify this technique when already out and unexpectedly (or otherwise) run into poor cell reception, by using an existing checklist in the app on which to base the new one.  It is important to remember in such cases that county boundaries are often filter-region boundaries and species that are expected in some counties (thus, not flagged by occurrence, alone) may be unusual in a neighboring county, which may cause some slight disconnects between what species one sees and the "allowable" list of species on the current active checklist on the app.

    Most eBirders understand the need to separate sightings in one county from those in another into different checklists.  While this is less of a problem in Wyoming than it is in Colorado (mostly due to the many fewer counties in Wyoming), both states host birding locations that cross county borders, with Yellowstone N. P. being the mother of all examples in the two-state region (heck, the Park even straddles multiple state borders!).  In Colorado, particular problem children birding sites include Chatfield S. P., Jumbo Reservoir, and Comanche N. G.  However, the single most-recalcitrant problem child is the area around Denver International Airport (DIA).

    The DIA problem was created when the airport was first proposed, because Denver County was allowed to annex a sizable chunk of what was then Adams County in order to build the airport and the access road (Peña Boulevard). This action created a long, snaking corridor of Denver cutting through Adams.  Were it not for Denver County's small size and its near-complete lack of native habitat, the DIA problem would not be a problem.  However, with birders' interest in county listing, this long snake of a Denver extension travels through some excellent habitat otherwise lacking in the county and providing access to species that have been extirpated from the original county boundary... such as Burrowing Owl.  The whole eBird-review problem here is based on the fact that this corridor of Denver is so narrow, just 1.3 miles wide at its narrowest, thus it is nearly impossible on a birding jaunt of the area to not cross into and out of Adams County, sometimes multiple times.  This all means that most (if not nearly all) eBird checklists submitted from the DIA environs cover an area claimed by multiple counties, something that is not "permissible" in eBird.

    In summary, I provide what I think are some reasonable guidelines on when to end the current eBird checklist and start a new one.
    • When a state boundary is crossed
    • When a county boundary is crossed
    • When crossing an obvious boundary between open habitat and wooded or forested habitat
    • When arriving at a birding location (particularly one that is an eBird hotspot) that has well defined borders and that is managed by a particular government agency or non-governmental organization (e. g., a state park, a national wildlife refuge, a private preserve)
    • When leaving a birding location (particularly one that is an eBird hotspot) that has well defined borders and that is managed by a particular government agency or non-governmental organization (e. g., a state park, a national wildlife refuge, a private preserve)
    • When leaving the "understood" area of an eBird hotspot, even if that hotspot lacks well defined borders (e. g., "Yellowstone NP--Midway Geyser Basin" or "Rocky Mountain NP--Endovalley")
    • When accruing 15 miles of distance in relatively homogeneous habitat in open country (such as in sage shrubsteppe, grassland, agriculture)
    • When accruing 5 miles of distance in relatively homogeneous forested habitat without significant (750 feet) elevational change
    • When accruing 2 miles of distance when encountering relatively significant elevational change (>750 feet, 1500 feet)
    • When accruing 1 mile of distance when encountering significant elevational change (>1500 feet)
    • When accruing two hours of observation (one hour would be even better)