The Changing Seasons
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CONTINENTAL ANALYSIS THE CHANGING SEASONS Charles D. Duncan which remained poised from northwest British Columbia nessed83 years of unusual weather. In reviewing the southeast to Colorado. Cold air from the storms moved I winterHAVEAN ChangingELDERLY Seasons NEIGHBORsection WHOofCLAIMS this journalTO HAVE for WIT- the southeast from the Great Plains bringingtemperatures 14øF past several years, I begin to see his point: each of these below normal to Minnesota, Wisconsin, Iowa, and Illinois, winters seems vastly different from the others and from and a hard freeze to central Florida, just after Christmas. anything like "an averagewinter." In 1981-1982, the season The stormsbrought heavy "lake-effect" snowsto the Great was described as "Endless Winter." In the East and North, Lakes states; Buffalo, always in winter a snowy city, it was marked by lowered avian survival. Raptorsincluding eclipsedprevious snowfalls to set a new monthly maximum Northern Goshawks, Rough-leggedHawks, Gyrfalcons, (68.4").To the west of the Pacific-Arcticfront, high pressures Hawk and Short-earedowls were presentin high numbers. aloft served to trap cold air at the surface and cause very Red-breastedNuthatches and CommonRedpolls were also persistent fog that shut out sunshine and warmth. Idaho widely reported as incurslye. recordedan awful 18øFbelow average,with 20 consecutive The fnllowing winter, 1982-1983, found E1 Nifio in the days below 0øF. There were few "winners" from this PacificOcean. This oceanicphenomenon produced an ex- weather pattern. In the southwest conditions were very ceptionallywet and mild winter acrossthe United States dry--not exactly a blessing there--and a few degrees and Canada. These conditions resulted in waterfowl, warmer than average. Curiously, the Canadian Prairie shorebirds,raptors, hummingbirds and passetineslingering Provinceswere also warmer than average, as was Alaska. later than average,but causedno irruption of borealseed- In the tropicalregions, where rainfall is much morevariable eaters. than is temperature, both the Hawaiian Islands and the Winter of 1983-1984 is remembered--for some of us this West Indies were exceptionally dry. memory is in our very bones--as "The Siberian Express," January is normally the coldest month in most places, with record-lowtemperatures in many areasduring De- but a long thaw this winter eliminated much of the snow cember and January.From an ornithologicalviewpoint, it cover previously deposited.Only the southeasternUnited was alsomemorable, with widespreadavian mortality, and States had temperaturesbelow average. It was very dry low numbersof individualsin someareas. More positively, over most of the continent and in a large land swath cen- at least for observers,was an influx of Asiatic strays like tered around Kansasand reachingwell into Texas had no Smew, Slaty-backed Gull (see this issue for all details), measurableprecipitation for the entire month. In contrast, Bramblings,Rustic Bunting, and SiberianRubythroat. Great the peripheries of the continent--Florida, New England Grey Owls irrupted and there was a moderate incursion and the Maritimes, the Pacific Northwest, British Columbia of boreal songbirds. and much of Alaska--had precipitation well above Lastwinter, 1984-1985, was not so easily characterized, average. This was enough, however, to bring snow cover and did not earn itself a nickname. Early winter was mild, north of a line running from New Jerseyto southern New January cold and icy, and February set record-high tem- Mexico. peratures in the East. Not surprisingly, many migrants, February's weather, complex in detail, is nonetheless especiallyshorebirds and warblers lingered well to the easyto summarize.It was warm comparedto averagesin north. The major irruptions were describedas food-, and most areas. Temperatures from south Texas (103øF) to not weather-related and involved White-winged and Red WashingtonState (73øF)were more appropriateto summer crossbills,Bohemian Waxwings, Mountain Bluebirds,and than winter. The regionsunaffected by the heat formed a Common Redpolls.Paul Lehman in his ChangingSeasons broadbelt acrossNew England,Great LakesStates, North- column, characterized them as western montane species ern Plainsand mostof SouthernCanada. Here temperatures moving into lowlands,south, and east. were normal, or at worst, slightly cooler than normal. Pre- The seasonjust past, the winter of 1985-1986, was also cipitation was generallywell above averageexcept in the not a simple one to describesuccinctly. For the majority non-coastalportions of the Southeastand alongthe Mex- of the regionsthis reportcovers, December was a very win- ican border. The only major snowstorm was a record- try month. November had been brutally cold in western breaker on Cape BretonIsland, Nova Scotia.The mostim- Canadaand northwesternUnited States.By mid-December portant meteorologicalfeature of the month was a series this coldhad beenbrought to abouttwo-thirds of the United of rainstorms on the Pacific coast from southern California States in a series of storms labelled "Alberta Clippers," to Oregon.The warm rains causedsnow to melt in the basedon their origin in a Pacific-Arcticfront and its as- higher elevations.The combinationof the delugesand the sociatedlow pressureareas over NorthwestCanada. Tem- snowmeltcaused severe flooding, especially in Sonomaand peratureswere well below averageto the eastof the front, Napa. Volume40, Number2 243 Historiansof sciencefind that as a d•sciplinematures it sachusettswere exemplary Yellow-throated Warblers passesthrough recogmzable stages: description, quantifi- were alsofound in Virginia(1st winter record),North Car- cation,and ultimately, prediction.Most of what is written olina, and even Arizona. The Southern Atlantic Coast Re- m this journal is descriptive:where birdswere and when. gionmanaged eight species of warblers,four earning "bold Eachyear in the ChristmasBird Counts, we participatein face" status.Florida had a dozenwintering species that an enormousquantitative endeavor,the largestsuch vol- were either unusual or especiallynumerous. The Town- unteer undertakingin all of science.But predictionis an- send'sWarbler at a naturecenter there must certainly have other matter entirely. Can one take the winter seasonre- increased the number of visitors. Most or all of these sur- ports of the precedingfew--or many--years, with the vived the Christmas week freeze. Louisiana too had a won- abovesummary of the pastwinter's weather, and predict derfulvariety of warblers.These may have been holdovers eitherthe broadtrends or the specificdetails of the records from the autumn hurricane season.It is clear, however, foundfollowing this column? I confess immediately that I that the numberand varietyof speciesthat remainednorth cannot.Ours, it seems,is still a very youngscience. The of the normalwintering grounds was substantial.In north- exerciseis notfutile, however, and I recommendit to any- ern California, an Elegant Tern was remarkable, as was a one seriouslyinvolved in examiningthe distributionand total of four speciesof Empidonaxflycatchers. In the same abundance of birds. It servesto focusattention on what we region, Prairie Warbler, American Redstart and Ovenbird need to know, and thus, information we need to collect. were unusual winter guests. For example,before I tried to predictthe whereaboutsof In the Northeast and Midwest, the number of Carohna seabirdsI would like to know the temperature and salinity Wrens overwintering is often indicative of the seasoffs values for the various bodiesof water involved. For birds hospitality.This winter they expandedin Maine and Que- of prey,I wouldneed to knowwhat the populationsof bec in the East, the Southern Great Plains in the West and small mammals were like well into the Arctic. For seed- essentiallyall "fringe" areasin between. The list of other or berry-eatersI would like informationon the food plants overwinteringand late migrantsis far longerthan can be m the breedingregion, in all areaswhere the bird breeds. examinedin this column.I invite you to delve into the (SeeAB 39(2):139,1985 andAB 37(3):276,1983 for more on reportsthemselves. There's far morewithin themthan my th•spoint.) Things get very complex very quickly. "prediction" would indicate. What would one say about a seasonwhere December was cold(except in the Southwest),followed by a warm anddry January, and then a verywarm and generally moist February?I would expectfew lingerersin mostregions, Rarities andan upsurgeof morenortherly birds in the Southwest. Ducksand speciesdependent on openwater shouldnot Whendisplaced birds are discussed in thiscolumn they havehad to movetoo far south,since the Januarythaw are often classified as "Eastern Birds West" or "Palearctic preventedmuch freeze-up. Boreal invaders, both raptors Birdsin theNearctic" etc. The assumption being that there andothers, should not havehad to moveespecially far is a pattern, and a common cause, to certain unusual b•rd rather.Finally, spring migration might start early in many movements.Even the choiceof the word "displaced"•m- regions,stimulated by the warmweather. Whatever you pliesa displacingagent, responsible for puttingall these do,do not stop here! With the exceptionof the lastone, all birds in boldfacedprint. When a seasonis known as "The these"reasonable" predictions were wrong. SiberianExpress" and Asiaticstrays abound, for instance, thisis probablyfitting. Often, however, the descriptionof thesebirds as "vagrants"seems more accurate:those who Late migrants