Cobirders: Since the question has come up privately a couple of times recently, I thought that I would respond publicly in this venue, as the information may be appreciated by all of Colorado's eBirders.
In the beginning, eBird was a very simple and simplistic world. From the start, though, the powers-that-were deemed it important to have filters for input data in order to flag entries that were atypical. These first filters were usually state-based, one-filter-per-state things that provided gross estimates of numbers acceptable for that state in each of the 12 months of the calendar. Chris Wood and I constructed that first Colorado filter. At that time, there were no non-species entries. That is, no spuhs, slashes, hybrids, subspecies. There were just species. As eBird has become more refined with much more capacity and capability, filters have become incredibly more complex. First, was the separation of the statewide filter with regional filters, for Colorado there five: Northeast, Southeast, Mountains, Northwest, Southwest. That, obviously, required some fine-tuning of each of those five filters to more-closely match each subregion's avifauna, such as not include Northern Bobwhite in the three western filters, exclude Gunnison Sage-Grouse from the two eastern filters. Second, was the addition of various non-species-level entries, the spuhs and the slashes (e.g., Semipalmated/Western Sandpiper, peep sp.). That meant going through each of the five then-extant filters and adding those non-species entries relevant to each filter, which was done on a fairly conservative basis -- only the really common non-specific entries were added, such as Snow/Ross's Goose and Cackling/Canada Goose. That wasn't too bad; tedious, but not too bad, and at that time, I was the only person working on Colorado's eBird filters. With the addition of Marshall Iliff as the final member of what is familiarly called the eBird trinity (Chris Wood, Brian Sullivan, and Marshall) that runs the program, eBird's abilities expanded further, with a more-in-depth taxonomy that was to cover the entire planet. Hybrids were added, many, many, many more non-species entries were added, even in the ABA-area, such that there are probably now more non-species-level entries available in the ABA area than species-level entries, some used exceedingly rarely, some widely used. Then, eBird tackled the 'April problem.' Those of us in the filter and record-review aspects of eBird (and I was, and am, doing both) had for years complained that the rigid monthly structure to the filters made for some major problems, with April being the poster child for such problems. In much of the ABA area, particularly the Lower 48, filter makers/editors had to decide to filter all occurrences of a migrant species that arrived in the filter region in the last few days of April, or allow all occurrences of such species, even in early April when they were unknown. In Colorado, MacGillivray's Warblers is an excellent case in point, with the vast bulk of migrants arriving in May, but with a very small number typically noted in the last week of April, but unknown in the state prior to the 22nd or so. The solution was to throw out the monthly framework, replacing it with, essentially, a weekly framework, but not tied to any particular idea of 'week.' While there are limits in all things -- and this new system's overarching limit was a maximum of 13 temporal filter periods per species per filter, the new system allowed chopping up, particularly, the short, intense spring migration of most migrant species into periods as small as five days, with each period allowed its own filter limit. Each filter period has a number that is 'permitted,' while any larger number of birds of that species in that time period would require review. As example, the in-construction Lincoln County filter has five filter periods covering the spring migration of Clay-colored Sparrow, allowing as many as 1 during 22-30 April, 9 during 1-7 May, 29 during 8-14 May, 15 during 15-21 May, and 9 during 22-31 May. While we could simply allow any number, doing so would mean that there was no way to catch data-entry errors of numbers, such as 10 entered instead of 1 or 355 entered instead of 35 (and I have seen both of these mistakes, which are easy to make when using the number pad on computer or laptop) made. In essence, a filter limit is the result of a decision about a tenuous balance between what might occur and data-entry errors, and such decisions need to be made for as many as 13 temporal periods in each of as many as 400 species and 175 non-species entries in each filter. While the new filter system allows an excellent amount of flexibility in constructing species- and location-specific filters, it is also much more complex and much more time-consuming to construct. It takes me something like 12-20 hours of tedious effort to make a new filter from scratch and not much less than that to use existing eBird data to fine-tune existing active filters. I use the temporal spread and abundance values from existing eBird data to create new filters or to modify existing filters. Depending upon the region, the filter includes some 300-400 species-level entries with 125-175 other taxa (spuhs, slashes, hybrids, etc.)., and multiple temporal periods per taxon for nearly every taxon. There are 28 active filters now covering eBird Colorado. I also have 16 filters in some stage of construction to enable better fit to particular counties currently covered by more-general, multi-county filters. The rationale for smaller-scale filters is generally self-evident, but as example, I constructed a filter for Phillips County a few years ago. I did that because Phillips County eBird data were being filtered by the general northeast Colorado filter, which, at that point, included Weld, Morgan, Washington, Kit Carson, Yuma, Phillips, Sedgwick, and Logan counties. Note that all of those counties but Phillips has at least part of a major water body in it. Thus, Phillips County data were allowed to include large numbers of waterbird species that were actually fairly rare there. However, just because a particular filter covers just one county does not mean that there aren't still difficult decisions about filtering to be made. Common Raven provides an excellent example of this challenge. The species is regular in small numbers in the far western part of Arapahoe County, but nowhere else in the county. It is also regular at the Rocky Mountain Arsenal NWR in the southwestern corner of Adams County, but is virtually unknown in the vast majority of the rest of Adams. Both Arapahoe and Adams are filtered by county-specific filters, so I have to decide whether to allow unfiltered Common Ravens from parts of those two counties where they do not occur or to have to review every entry of Common Raven, even those in the parts of the counties in which they are known to occur with regularity. As more data are entered in eBird, the data set for a particular filter region becomes more robust and allows for more-precise filter limits and temporal periods, and I am constantly trying to incorporate fine-tuning of existing filters. However, I also am endeavoring to construct new filters to get the review of data from counties like Lincoln out of the hands of more-general filters that are not particularly effective for the county (currently in the Southeast filter, which also includes Baca, Prowers, Kiowa, Bent, Otero, and Crowley counties). Thus, you may encounter remnants of previous filter strategies when entering data into eBird, simply because I have not found the free time to completely revamp older filters. Please bear with me on these minor problems while I'm still dealing with larger ones, as 100s and 100s of hours that I spend on eBird filter and review tasks is a volunteer effort. However, feel free to drop me a line about any particularly egregious filter problems. Current Colorado eBird filters: Adams Arapahoe Archuleta, Dolores, La Plata, Montrose, San Miguel Boulder Broomfield, Denver Chaffee Clear Creek, Gilpin Custer Delta, Mesa Douglas El Paso Elbert Fremont Huerfano Jefferson Larimer Las Animas Montezuma Northern Mountains (Grand, Jackson, Lake, Park, Summit, Teller) Northeast (Kit Carson, Logan, Morgan, Sedgwick, Washington, Yuma) Northwest (Eagle, Garfield, Moffat, Pitkin, Rio Blanco, Routt) Phillips Pueblo San Juan San Luis Valley (Alamosa, Conejos, Costilla, Rio Grande, Saguache) Southeast (Baca, Bent, Cheyenne, Crowley, Kiowa, Lincoln, Otero, Prowers) Southwest montane (Gunnison, Hinsdale, Mineral, Ouray) Weld Filters in construction Archuleta Baca Bent Cheyenne Crowley, Otero Dolores, Montrose, San Miguel Grand, Jackson Kit Carson, Yuma La Plata Lake Lincoln Ouray Park Prowers Summit Teller Tony Tony Leukering Largo, FL http://www.flickr.com/photos/tony_leukering/ http://aba.org/photoquiz/ -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. 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