Ola from Costa Rica! I would like to announce my intent this spring to file irregular reports on the passage of neotropical migrants as they leave or pass through Costa Rica. SPRING MIGRATION I have provided, at the end of this email, a list of the principal species that winter here in Costa Rica at our elevation (4000 feet) and position on the Pacific slope (Cordillera de Tilaran near Monteverde), and those that commonly migrate through here. I have indicated the most common ones with asterisks (*). Over the next two months or so, I will try to report when migrants are passing through (or appear to be leaving) and indicate whether numbers appear high (just a general impression) and when their numbers appear to have peaked. MIGRANTS THIS PAST FALL AND WINTER I have been very lax in reporting neotropical migrants here in our location in Costa Rica this fall and winter. The chief reason has been the general lack of activity by most migrants in our area. Aside from a few common regulars (Summer Tanager, Wilson?s Warbler, Black-and-white Warbler), numbers have been very low when compared to the previous winter. Whereas last winter most insectivorous feeding flocks consisted of about 50% local species and 50% neotropical migrants, this year about 90% of the birds in these small flocks are local species (chiefly Golden-crowned Warblers, Common Bush-tanagers, Slate-throated Redstarts, Olivaceous Woodcreepers, etc.). At times all of the usual neotropical species have been mixed into these flocks, but only in very low numbers and only occasionally (Yellow-throated Vireo, Golden-winged Warbler, Blue-winged Warbler, Tennessee Warbler, Black-throated Green Warbler, Townsend?s Warbler). There are several hypotheses I propose for this rather drastic change between winter 2004-5 and this past winter: 1) There are fewer migrants in Costa Rica this year for various reasons, possibly the extremely high number (and high intensity) of hurricances during fall migration?I personally do not think this is very plausible as I have seen good numbers of the same species at lower elevations. 2) There was excessive rainfall here throughout September and October (42 out of 46 days the sun did not come out at all and it rained pretty much 24 hours a day?a result of the incredible hurricane activity in the southern Caribbean during those months). This year was in stark contrast to the previous years? weather during these months, when rainfall was unusually low and most days were sunny. This year?s conditions resulted in terrible feeding conditions for newly arriving insectivorous neotropical migrants, who therefore (according to this hypothesis) chose to set up there winter feeding territories elsewhere (probably at slightly lower elevations and/or on the Caribbean slope where there was less rain). 3) The excessive rainfall in Sept. and Oct. resulted in very low reproductive success among many insect species, since many attempt to mate in the air and continuous rainfall day and night can make this very difficult. This resulted in a very low supply of insect larvae and adults for months after the fall rains. In fact, we have observed very few insects eating our orchard trees, native trees, or in our vegetables this winter compared to the year before. I strongly believe that both hypotheses 2 and 3 are both together the causes of the change, though I have no hard data to back that up. This, to me, demonstrates the tremendous potential impact that climate changes can have on bird behavior. At the same time, it hints at the adaptability of most species to such changes when such adaptations are possible?for example, moving to a lower elevation or to a different slope position. Of course, one should note the caveat of ?when such adaptations are possible.? Hypothesis 2 also indicates that once they chose a general wintering territory, many birds have a fair amount of faithfulness to these territories. Whether my speculations are correct or not, it certainly has been an interesting year here, though I prefer it when there are more species rather than less! Here is my list of common neotropical migrants here, which I hope to report on: WINTER RESIDENTS (and Passing Migrants) LEAVING: Wood Thrush *Yellow-throated Vireo *Black-and-white Warbler Worm-eating Warbler *Golden-winged Warbler Blue-winged Warbler *Tennessee Warbler Yellow Warbler *Townsend?s Warbler *Black-throated Green Warbler Ovenbird Kentucky Warbler *Wilson?s Warbler *Baltimore Oriole Eastern Meadowlark *Summer Tanager MARCH MIGRANTS: Broad-winged Hawk *Ruby-throated Hummingbird Barn Swallow *Northern Rough-winged Swallow *Swainson?s Thrush La. Waterthrush APRIL MIGRANTS: Eastern Kingbird Olive-sided FC Eastern Wood-Pewee Empidonax spp. (chiefly Alder, Willow, Yellow-bellied) Philadelphia Vireo *Red-eyed Vireo *Blackburnian Warbler Canada Warbler Scarlet Tanager *Rose-breasted Grosbeak Indigo Bunting Dev Joslin Monteverde, Costa Rica =================NOTES TO SUBSCRIBER===================== The TN-Bird Net requires you to sign your messages with first and last name, city (town) and state abbreviation. You are also required to list the count in which the birds you report were seen. The actual date of observation should appear in the first paragraph. _____________________________________________________________ To post to this mailing list, simply send email to: tn-bird@xxxxxxxxxxxxxx _____________________________________________________________ To unsubscribe, send email to: tn-bird-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field. ______________________________________________________________ TN-Bird Net is owned by the Tennessee Ornithological Society Neither the society(TOS) nor its moderator(s) endorse the views or opinions expressed by the members of this discussion group. 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