Thursday, February 17, 2011

More occurrence maps being published

We haven't posted much here recently, and are sorry for this. The winter doldrums have been a time where we have been working hard on several things at eBird, and we'll be sharing these with you here soon.

One of these has been gearing up for publishing lots more occurrence maps. Since the last post 15 December we have posted 16 new maps (involving 17 species!). Over the next month we plan to put up a lot more, so please check in to the Occurrence Maps page regularly and watch for the *NEW* ones!

As always, we welcome comments on the maps here. New species since 15 Dec include:

Scissor-tailed Flycatcher (Tyrranus forficatus)
Horned Lark (Eremophila alpestris)
Harris's Sparrow (Zonotrichia querula)
Lesser Goldfinch (Spinus psaltria)
Rock Wren (Salpinctes obsoletus)
Orchard Oriole (Icterus spurius)
Pacific/Winter Wren (Troglodytes pacificus/hiemelis)
White-eyed Vireo (Vireo griseus)
Painted Bunting (Passerina ciris)
Black-throated Gray Warbler (Dendroica nigrescens)
Yellow-throated Warbler (Dendroica dominica)
Wood Thrush (Hylocichla mustelina) [not animated -- fine scale]
Kentucky Warbler (Oporornis formosus)
Pine Warbler (Dendroica pinus) [not animated]
Mountain Bluebird (Sialia currucoides)
Dusky Flycatcher (Empidonax oberholseri)

eBirders have provided some great questions and comments about the strengths and weaknesses of these maps. These really help us to refine them in the future. We look forward to more feedback!


  1. Both Yellow-throated and Kentucky Warbler maps show occurrence in the Adirondacks which is not accurate.

  2. cnybirder: Indeed. We are aware of these occasional issues, which seem especially acute near the northern limits of the ranges of "southern warblers" and near other frontiers where dense data (i.e., Washington D.C-New-York-Boston corridor) give way suddenly to sparse data (i.e., Adirondacks, central/northern Maine). Northern Minnesota and south Florida are two other regions with consistent issues, which we continue to try to understand better. We think Florida is related to the NLCD (National Land Cover Data) available for there and how the forests are classified. There is now question, however, that more data will allow us to look at finer scale and to make these more accurate.

    See the comments in the accounts, which specifically address your comment.

    Kentucky Warbler: As is the case with some of these maps, there are some anomalies that appear to be caused by the model making incorrect assumptions about where the species occurs. A notable one on this map is the bright spots in west-central Texas that appear in April, with a large one just east of Big Bend appearing in June and July. This area does not get Kentucky Warblers with regularity, and this is certainly a case where a finer-scale model would compensate for these erroneous predictions--but that requires ever more data (the smaller the scale, the more data needed). A similar process may be driving the occurrence shown for the Adirondack Mountains of northern New York--Kentucky Warblers do not occur here either. As the eBird data set continues to grow, we are confident that these anomalies will become rarer and rarer.

    Yellow-throated Warbler: [Note: The faint Adirondacks signal is an artifact of sparse data and how the model attempts to compensate for that. This seems to be due to the association of Yellow-throateds with forest, and evergreen forest in particular, in southern parts of the same regional model. As the dataset grows, we will be able to use smaller and smaller regions for the models which will make issues like this go away. For now, the predictions in the Adirondacks (where data are sparse) are drawing from nearby areas, where Yellow-throateds do occur. This is a known issue and a research direction for us to minimize it.]

  3. I'm a huge fan of these occurrence maps, and the animations are something that I've visualized since the first day I saw The Weather Channel and decided that they needed to present a "bird migration forecast." I guess I've been waiting about 25 years for these.

    Amid all the requests for "do this species or that species next," I'm going to add my request for Black-throated Blue Warbler. I'm particularly interested in the routes this species takes during migration.

    Link to my blog bragging about eBird occurrence maps: