Identification Tips for Tricky Species Pairs: Western & Clark's Grebes
In the world of ornithology, there exist what I like to think of as species pairs: two very closely related species that look very similar and cause no small amount of frustration and confusion for the beginning birder. Some species become familiar and easily distinguishable from each other with practice, while others remain much more confusing, even to experts. Some species pairs are best told apart by range and voice alone!
A familiar pair in California during the winter months, Snow Geese and Ross's Geese are one such example of two species that share the same range and may even be seen together. Though at a glance they look almost the same, their physical differences lie in their size and proportions (bill proportions and head shape especially) and a few other slight differences. In field guides, they look impossibly similar, but in real life, the differences are clear: each species has a completely unique "feel" (known to birders as "jizz," referring to all the characteristics of a bird which, when taken together, make up the overall impression of that species). Downy and Hairy Woodpeckers are two other quite similar species, best distinguished by proportions.
How can I tell a bird is a Ross's Goose (left) rather than a Snow Goose (above)? I just know it is one, without even thinking about size, head shape, relative bill size, the shape and color of the bill or absence/presence of a "grin patch"! It just looks and feels like a Ross's Goose. The same goes for a Downy vs. Hairy woodpecker. It comes with practice and familiarity. (Maybe it's a little like how parents and close relatives can tell apart twins so easily, while other acquaintances struggle.)
Other species pairs are best told apart by range, like Nuttall's and Ladder-backed Woodpeckers, or Pacific-slope and Cordilleran Flycatchers (all birds of the Western United States). In California, the ranges of the very similarly-patterned and sized Nuttall's and Ladder-backed Woodpeckers overlap very little, and it's almost safe to assume that if you're in an oak or riparian area, it's a Nuttall's, while the Ladder-backed is restricted to dry desert areas of the southeastern part of the state.
Field guides generally say that Pacific-slope and Cordilleran Flycatchers are "essentially identical" to each other in appearance and are best told apart by range and voice. West of the Sierra-Cascade axis, on the Pacific slope, you're likely to find the Pacific-slope Flycatcher, while the range of the Cordilleran Flycatcher is restricted to areas east of this axis. (But the line is entirely arbitrary and their ranges do overlap, the Pacific-slope Flycatcher ranging east into Cordilleran territory.)
In one of the most confusing cases of species pairs, it's only possible to distinguish an Allen's from a Rufous Hummingbird with any certainty by looking at a male during the breeding season, on his breeding ground, and getting a good look at his tail feathers. During migration, you can pretty much forget telling these two apart with absolute certainty, unless you're an expert at measuring tail feathers and have the good fortune of holding a male Rufous/Allen's Hummingbird in your hand in order to do so.
Luckily for those new to birding, these confusing pairs are the exception, not the norm, and with practice it does get easier!
Western and Clark's Grebes are two species whose ranges and habitats overlap; they may even be seen paddling together on the same lake! And while at first glance one may think these two birds are the same species (see the photo below), there is one easy way to tell these two apart (well... at least during the breeding season...)
First, we'll compare the black caps of the two birds above, which is the easiest, most obvious way to differentiate between Western and Clark's Grebes. The black cap of the Clark's Grebe ends well above the eye, as seen in the bird in the left or foreground of the photo above. On the Western Grebe, the black cap extends all the way to the eye and below.
Bill color differs slightly between the two species as well. Clark's Grebes have brighter yellow or yellow-orange bills, while the bills of Western Grebes tend to be a bit more olive-yellow in color.
The two species often show subtle differences in overall color as well, with the Western Grebe being darker than the Clark's Grebe. Both species have black stripes running down the back of their necks, which can be used as an aid in identification as well. The Clark's Grebe has a thin stripe (below left), while the Western Grebe has a thick stripe (below right).
Hopefully these tips will help you confidently identify your next Western or Clark's Grebe!
I will note that Sibley's field guide states that during the winter, some birds that appear intermediate between the two species are unidentifiable... and may actually be hybrids. See this post on hybrid gulls for more identification tips for confusing groups of birds!
A familiar pair in California during the winter months, Snow Geese and Ross's Geese are one such example of two species that share the same range and may even be seen together. Though at a glance they look almost the same, their physical differences lie in their size and proportions (bill proportions and head shape especially) and a few other slight differences. In field guides, they look impossibly similar, but in real life, the differences are clear: each species has a completely unique "feel" (known to birders as "jizz," referring to all the characteristics of a bird which, when taken together, make up the overall impression of that species). Downy and Hairy Woodpeckers are two other quite similar species, best distinguished by proportions.
How can I tell a bird is a Ross's Goose (left) rather than a Snow Goose (above)? I just know it is one, without even thinking about size, head shape, relative bill size, the shape and color of the bill or absence/presence of a "grin patch"! It just looks and feels like a Ross's Goose. The same goes for a Downy vs. Hairy woodpecker. It comes with practice and familiarity. (Maybe it's a little like how parents and close relatives can tell apart twins so easily, while other acquaintances struggle.)
Other species pairs are best told apart by range, like Nuttall's and Ladder-backed Woodpeckers, or Pacific-slope and Cordilleran Flycatchers (all birds of the Western United States). In California, the ranges of the very similarly-patterned and sized Nuttall's and Ladder-backed Woodpeckers overlap very little, and it's almost safe to assume that if you're in an oak or riparian area, it's a Nuttall's, while the Ladder-backed is restricted to dry desert areas of the southeastern part of the state.
Field guides generally say that Pacific-slope and Cordilleran Flycatchers are "essentially identical" to each other in appearance and are best told apart by range and voice. West of the Sierra-Cascade axis, on the Pacific slope, you're likely to find the Pacific-slope Flycatcher, while the range of the Cordilleran Flycatcher is restricted to areas east of this axis. (But the line is entirely arbitrary and their ranges do overlap, the Pacific-slope Flycatcher ranging east into Cordilleran territory.)
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| My best attempt at capturing a distant Pacific-slope Flycatcher last weekend at Montana de Oro State Park (San Luis Obispo county). Cordilleran Flycatchers look pretty much exactly the same, and until the 1980's the two were considered one species, the Western Flycatcher. |
In one of the most confusing cases of species pairs, it's only possible to distinguish an Allen's from a Rufous Hummingbird with any certainty by looking at a male during the breeding season, on his breeding ground, and getting a good look at his tail feathers. During migration, you can pretty much forget telling these two apart with absolute certainty, unless you're an expert at measuring tail feathers and have the good fortune of holding a male Rufous/Allen's Hummingbird in your hand in order to do so.
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| While the photo quality is poor, I feel confident calling this guy an Allen's Hummingbird, as his back showed green and he was seen in late May in coastal chaparral (Montana de Oro State Park, San Luis Obispo county), quintessential breeding habitat for this species. |
Luckily for those new to birding, these confusing pairs are the exception, not the norm, and with practice it does get easier!
Western and Clark's Grebes are two species whose ranges and habitats overlap; they may even be seen paddling together on the same lake! And while at first glance one may think these two birds are the same species (see the photo below), there is one easy way to tell these two apart (well... at least during the breeding season...)
 |
| Clark's Grebe (left/foreground) & Western Grebe (right/background) |
First, we'll compare the black caps of the two birds above, which is the easiest, most obvious way to differentiate between Western and Clark's Grebes. The black cap of the Clark's Grebe ends well above the eye, as seen in the bird in the left or foreground of the photo above. On the Western Grebe, the black cap extends all the way to the eye and below.
Bill color differs slightly between the two species as well. Clark's Grebes have brighter yellow or yellow-orange bills, while the bills of Western Grebes tend to be a bit more olive-yellow in color.
The two species often show subtle differences in overall color as well, with the Western Grebe being darker than the Clark's Grebe. Both species have black stripes running down the back of their necks, which can be used as an aid in identification as well. The Clark's Grebe has a thin stripe (below left), while the Western Grebe has a thick stripe (below right).
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| Clark's Grebe - thin hind stripe |
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| Western Grebe - thick hind stripe |
I will note that Sibley's field guide states that during the winter, some birds that appear intermediate between the two species are unidentifiable... and may actually be hybrids. See this post on hybrid gulls for more identification tips for confusing groups of birds!
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