So, I am not really going to make a prediction, but comment on some other predictions
Ben Sampson came up with a very thoughtful list, though I would scratch Barnacle Goose (and Mute Swan, mentioned by others) for reasons discussed below.
Of the birds on Ben's list, CALIFORNIA QUAIL has to be #1, as it that species has been reported by several good observers at various Moffat County locations. The only thing missing is documentation. I (and others) have tried to find this species, without success, but it is just a matter of time.
Others, such a GOLDEN-FRONTED WOODPECKER have so many records so close to CO, it is amazing that CO has not had one yet.
The birds on Ben's list that I think of as relatively low likelihood are WHITE WAGTAIL and BROWN-HEADED NUTHATCH
BARNACLE GOOSE AND MUTE SWAN.
BARNACLE GOOSE:
I am forever mystified by people's fascination, including some BRC's, with Barnacle Goose occurring naturally in the interior of the USA. It is a species that is fairly common in private aviculturalist collections. The scattering of records (looking at eBird data is misleading, as different states have different policies on this species, so nothing in MI and many in IL) across the continent does not bespeak a natural phenomenon. Greenland GWF Goose and Pink-footed Goose have a somewhat similar distribution as Barnacle Goose, but are rare in captivity. Those two geese have not been recorded west of Indiana, and for the most part, with very very few records west of central Pennsylvania.
Though it is possible that a wild Barnacle Goose could occur in CO, that possibility is overwhelmed by the possibility of an escaped bird wandering here. Think of Colorado's Emperor Goose (a far better candidate for natural vagrancy in my opinion), which was shown to not be of wild origin.
MUTE SWAN: I am not certain what "Has shown up in different configurations each year" suggests. One would expect a natural vagrant to have a somewhat regular pattern, not scattered. Scattered would suggest escapes or wandering individuals fetching up in popular birding places at irregular intervals.
In northeastern CO, the pattern has been consistent. There is a small population, very likely <10, of adult birds that show up in various spots in and around Greeley occasionally roaming south to Longmont or e. Larimer County. The farther from Greeley, the less numerous the records. Evidence for breeding is extremely limited, and adults can live 30 years in the wild. This species is abundant in captivity. There is no significant established population within 100s of miles of CO.
Given
1) no nearby established breeding population
2) no evidence of regular breeding within CO,
3) a known small population of non-reproducing (or nearly so) adult birds
4) high likelihood of ongoing escapes from captivity
I see little reason to add this species to a list of naturally occurring or established species in CO.
We should still track reports of both Barnacle Goose and Mute Swan, especially as the latter has the potential of becoming established. But not in the near future.
Good Luck to us All in 2018 (and beyond!)
Steven Mlodinow
Longmont CO
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