| UID |
|
| Digital Object Type |
Rare birds documentation form |
| Content DM Link |
https://n2t.net/ark:/87292/w9c824g9h |
| Type |
Text |
| Description |
Rare bird documentation form for a Thayer's Gull at Cone Marsh in Louisa County, IA on February 27, 1983. |
| Related Genres |
Field notes |
| Sort Date |
1983-02-27 |
| People / Organizations |
|
| Time |
11:10 AM |
| Rights |
This Item is protected by copyright and/or related rights. However, for this Item, either (a) no rights-holder(s) have been identified or (b) one or more rights-holder(s) have been identified but none have been located. If you have any information that can contribute to identifying or locating the rights-holder(s) please notify the Iowa State University Library Digital Initiatives Program (digital@iastate.edu). (Rightsstatements.org InC-RUU 1.0). The original object is available at the Iowa State University Library Special Collections and University Archives (archives@iastate.edu). |
| Data Access Rights |
http://vertnet.org/resources/norms.html |
| Data License |
http://creativecommons.org/publicdomain/zero/1.0 |
| Collection |
Iowa Ornithologists' Union | MS 166 |
| Box |
34 |
| Folder |
35 |
| Contributing Institution |
Iowa State University Library Special Collections and University Archives |
| Creator / Author |
Newlon, Michael C. |
| Contributors |
Newlon, Carol S. |
| Topics |
Birds--Identification Ornithology Rare birds |
| Birds |
Thayer's Gull |
| Locations |
Cone Marsh Wildlife Management Area |
| Map |
|
| Verbatim Locality |
NE side Cone Marsh Louisa Co IA |
| Location Remarks |
The documentation forms do not include georeferences |
| Habitat |
freshwater marsh with considerable open water |
| Extent |
1 page |
| Language(s) |
eng |
| Bibliographic Citation |
|
| Information Withheld |
|
| Individual Count |
1 |
| Occurrence Remarks |
The documentation form by Michael Newlon is the only one submitted and forms the basis of this record. Other observers include Carol S. Newlon. | Elimination of similar species: proportions, uniformly pale primaries would rule out herring; size/build rules out imm. glaucous. Bill much less heavy than imm. glaucous-winged. Remaining question is whether this bird is (over) a Thayer's Gull or a Kumlien's gull, presently considered separate species but widely suspected of being conspecific. Thayer's is extremely variable, and the limits of its variability are not well known, especially for imm. plumages. [Dwight says of his series of ad. thayeri, 'no two are alike'. It seems probable that there is clinal variation from west to east (thayeri - kumliesi [sic] - nominate glaucoides) and even possible that thayeri interbreeds with argenlatus at the western end of its range.] In addition several plumage descriptions in the literature may be assigned to birds of [illegible] age. Be that as it may: L. glaucoides glaucoides is supposed to have pale warm-brown primaries as a 1-W & paler, nearly whitish areas as a 2-W (though photos in grant's [sic] book show one 2-W with pale-brown primaries concolor with coverts). L. glaucoides kumlieni (in Dwight's plates) is assigned v. pale primaries as a 1-W, with slightly darker outer webs; would look uniform pale grey at any distance. His 2-W has darker primaries, again with slightly darker outer webs [I suspect these assignments should be reversed.] L. thayeri in published description is supposed to have darker primaries still, though not so dark as those of imm. Herring gulls, and lacking contrast with mantle. However some west coast thayeri-type gulls are very pale - though their back color is grey-brown rather than the warmer pale tan of L. glaucoides. (It is possible that these are really kumlieni but little data exists.) It is the similarity of the Cone Marsh Bird to one I photographed in Cal. that convinced me to classify it as thayeri - though kumleni cannot be unequivocally ruled out | The original documentation form event lasted from 11:10:00/12:30:00. |
| Occurrence Status |
present |
| Field Number |
|
| Event Remarks |
Viewing Conditions: 100 yds - 200 yds; light at ~ 90 degree angle, not optimal. High hazy cloud - no shadows. 8x40 binocs, 25x60 scope. |
| Supporting Documentation |
Grant, PJ. Gulls: a guide to identification. Cambridge, MA: Academic Press. | Dwight J. The gulls (Laridae) of the world; their plumages, moults, variations, relationships and distribution. Bul of Am Mus Nat Hist. 1925; 52(3):63-408. |
| Date Digital |
15 Dec 2017 |
| File Type |
image/jpeg |
| Hardware / Software |
Epson - sheet feed |
