[CT Birds] Knowing a Leopard By Its Spots
ls.broker at cox.net
Fri Oct 2 16:25:15 EDT 2015
My subscription to Birds of North America Online is justified whenever I see a bird species in the field that generates interest and admiration and commands further learning. Also, there are times when the ctbirding listserv encourages me to seek a deeper understanding of a species’ life history. This past Tuesday, I spent an hour with the Commonfields at Mansfield Center juvenile Purple Gallinule. What a fascinating bird to observe! I’ve kept up with the ctbirding thread on this bird and have to say that there have been some extremely well written, thoughtful, and informative comments about this vagrant in Connecticut. Perhaps our moderator will allow further discussion on this subject if we don't exhaust all lines of thought and if we manage to avoid going toxic.
So, what can be learned from BNA Online? I’ve extracted several aspects of Purple Gallinule’s life history strategies here. Richard L. West and Gene K. Hess wrote the BNA Online species account for Purple Gallinule.
1. Range: Members of the Family Rallidae are well known for their tendency to produce vagrants; “the champion vagrant of this family may well be the Purple Gallinule.”
2. Breeding Range: While the regular breeding range of Purple Gallinule is along the Atlantic Coast from South Carolina to the Gulf States Coastal Plain, extralimital breeding is known as far north as Tennessee, Illinois, and Ohio and along the coast to Virginia, Maryland, and Delaware.
3. Other Records: Purple Gallinule is known to migrate or disperse in North America as a casual or accidental species as far north as Newfoundland, Labrador, Nova Scotia, New Brunswick, Quebec, and Ontario. “This vagrancy may partially result from individuals being carried astray by wind.” From the species introduction: “This vagrancy trait may make it an effective pioneer to new wetlands as far north as Illinois.”
4. Winter Range: Temperate and tropical areas from Florida and northern Mexico south throughout its breeding range: West Indies, Central America, and South America to northern Argentina.
5. Fall Migration (pertains largely to the regular breeding range): Late August, September, and early October. “Final departure obscured by stragglers into November or casually later.”
6. Extralimital Records: Most in North America occur in April , May, and October, “during normal migration period. Small number occur in midwinter.”
7. Migratory Behavior: Strong fliers when migrating, using substantial heights. “Migrants meeting cyclonic storms especially prone to being blown well beyond normal range.”
8. Diet: “Varies greatly with seasonal and local availability, but over time, plant food predominates over animal.” Flowers, fruits are the major food items. Quantitative: 71% plants (seeds), 29% animal matter (aquatic invertebrates, beetles, dragonflies, spiders, occasionally frogs).
9. Life Span and Survivorship: No information.
10. Causes of Mortality: Predation, human-related causes.
11. Population Regulation: “Severe drought and draining of favored bodies of water may be chief limiting factor.”
12. Management/Conservation Status: Pertains only to regular breeding range (lower Atlantic Coast and Gulf Coast states): habitat protection critical.
Now, here are two field observations of the Commonfields Purple Gallinule and a personal comment:
13. In spite of the drooping left wing, the bird moved very effectively on the mud flats, alternating slow locomotion walking and hopping with occasional bursts of speed to out-of-sight areas. It foraged near-continuously during the hour of observation. While there’s no certainty that it can overwinter successfully, I suspect that it’s healthy enough to see in the New Year. Other rallied species persist in southern New England into January and occasionally February.
14. During a two-minute timed interval of observation, the Purple Gallinule jerked its tail upward 95 times, usually with single tail twitches but occasionally giving quick-spaced double tail twitches. Purple Gallinule is the ultimate twitch bird.
15. I admire greatly the work of the wildlife rehabilitators for their humane dedication to caring for injured birds and other vertebrates, and I trust implicitly their efforts at providing care for the wildlife brought to them. The human impact on the natural environment is so pervasive that the wish to let nature run its course now rings rather hollow.
Finally, be sure to read Frank Gallo’s excellent article, “Purple Gallinule; the Deceptive Vagrant. Its Occurrence in Connecticut, published in The Connecticut Warbler, Volume V, Number 4, pages 43-46 (with cover photo by Ray Schwartz) at this link: http://www.ctbirding.org/Warbler/CTWarblerVolume05.pdf <http://www.ctbirding.org/Warbler/CTWarblerVolume05.pdf>
Steve Broker, Cheshire
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