Where Do Northern ("Baltimore") Orioles Spend the Winter?
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Where do Northern {"Baltimore")Orioles spend the winter? Spencer G. Sealy Department of Zoology University of Manitoba Winnipeg, Manitoba RST 2N2 heforested dune ridge that separates Lake Manitoba Results and Discussion from Delta Marsh, Manitoba, has been the focus since 1974of an ongoinginvestigation into the ecologyof a com- An s¾male 1861-035291, bandedand color marked on munity of denselynesting species of insectivorousbirds the dune-ridge study area on 20 June 1977, was found and one dove species(study area and bird community deadby N. Hansonon 10 July 1977,near Goodridge,Min- describedby Sealy 1980a, b; MacKenzie 1982; MacKen- nesota,about 245 km southeastof the study area. The im- zie et al. 1982). Since this work began, 2,191 Northern plication of this recovery is that SY males leave the Orioles of the "Baltimore" subspecies(Icterus galbula breedinggrounds not long after their prebasicmolt has galbula]have been banded,and in most casesuniquely begun (see Sealy 1979), presumably destined for their color marked. Two of these orioles were encountered off wintering areas.The lack of mist-net captures,repeats, the foresteddune ridge. One recoveryoffers a clue to and sightingsof SY maleson the studyarea after mid-July where individualsof this populationspend the winter. The (Table2) alsosuggests strongly that thesemales leave the otherrecovery, supported by observationsof color-marked study area, whereas it is known that the ASY males and individualsand mist-netcaptures during the late nestling AHY females complete their prebasic molts before andpost-breeding periods on the studyarea, suggests that migrating south in late August (Sealy 1979). It is not SY malesleave the studyarea in mid-summer,presumably known whether the prebasicmolt of SY males is inter- destined for their wintering grounds,up to one month ruptedwhile they migratesouth, and completedafter they before the ASY males and AHY females migrate arrive on the wintering grounds. Why do SY male southward. "Baltimore"Orioles leave the breedinggrounds about one monthor more beforethe adults?As such,the early depar- The recoveriesmentioned above are detailed in the pre- ture of these males from the dune-ridgeforest, and pro- sent paper. In addition, the recordsof the encountersof bably also other areas,occurs before the collapseof the banded "Baltimore" Orioles (Table 1), furnished by the food supply (see Sealy and Biermann 1983). Thus, it is Migratory BirdsBranch, Canadian Wildlife Service,which unlikely that suchearly fall migrationsouthward is direct- date back to 1924, provide additional information on ly relatedto foodavailability on the breedingground (see where "Baltimore" Orioles spend the winter. I have alsoRappole et al. 1979).Sealy (1979) argued that because broken down these encountersas follows: (1) orioles at leastsome SY malesnest successfullyon the studyarea, bandedduring springmigration or the breedingseason with their numbersvarying from year to year (Sealy,un- and recoveredwithin the subspecies'known wintering pub. data), it is possiblethat those that move southward range (see Fig. 1) during the following or a subsequent early and while molting did not breed or were failed winter, (2) birds banded in the wintering range and breeders. The continued absence of SY males after mid- recoveredduring the followingor a subsequentbreeding July (Table2) suggeststhat indeedall of thesemales leave season,and (3) birds bandedon the wintering grounds early. Such early departure from the breeding ground which repeated at the same site or returned there in a should mean that these males arrive first on the winter- subsequentwinter. Recoveriesof oriolesfrom the eastern ing ground, but confirmation of this is needed. Sealy United Stateswhere their relatively recent presencein (1979) believedthat the lessexperienced males may be winter apparentlyhas been influenced by the provision- better able to compete for food and spaceon the winter- ing of food at feedingstations (see Erickson 1969) have ing groundsif they arrived beforethe ASY males,as Mor- been ignoredin this analysis. ton (1976)argued for the early-migratingYellow Warbler (Dendroicapetechia]. Age-related differences in the abili- ty to hold territorieson the wintering groundshave been found in Yellow Warblers (Morton 1976) and Dark-eyed Juncos(Junco byemalls] (Ketterson and Nolan 1979) and are probablycommon in many passerinespecies (see also Ewald and Rohwer 1980). Page 12 North American Bird Bander Vol. 10, No. 1 Figure 1. Breedingand wintering distributionsof the "Baltimore" Oriole. Distributional data upon which this map is basedare from: A.O.U. Check-list{1983}, Bond {1960},Dickey and van Rossera{1938}, Paynter {1955},Godfrey {1966},Johnsgard {1979}, Land {1970},Meyer de Schauensee{1970}, Monroe {1968},Edwards {1972}, Ridgely {1976}, Rising {1970, 1983}, Salt and Salt {1976},and Slud {1964}. This subspeciesis a rare transient through the western portion of the West Indies {Bond1960} and apparentlyan occasionalwinter resident{Lack 1976}. Inset: Major portion of the wintering range of the "Baltimore" Oriole showingwhere and how many recoveries{numbers in circles}have been obtainedof individualsof this subspeciesbanded on their breedinggrounds {see also Table 3}. One of the two Mexican recoverieswas obtained in the south central part of the country, where this subspeciesis known to occurin winter. The exactlocation in Mexico of the the other recoveryis not known. Fig. 1 BREEDING RANGE WINTERING RANGE MEXICO BELIZE HONDURAS / NICARAGUA GUATEMALA/ COSTA RICA EL SALVADOR PANAMA Jan.-Mar. 1985 North AmericanBird Bander Page 13 Table 1. Encounters with banded Northern Orioles, An SY male (861-03511),banded and color marked on 18 1924-1979. June 1977, was reported by Alfredo Garcia at Desconocido,Guatemala, in January,1981. This male was Encounters*** about 5V2 years old when reported and had not been Number**number Withinsame 10'grid number outside 10'grid of recapturedduring the interveningyears on the Manitoba Number of oflatitude and longitude of latitude and longitude Subspecies*banded encounters where banded (% of tota) wherebanded (% of total) study area. I did not ascertainwhether it nested in 1977, althoughmany $Y males did that year on the study area Baltimore45,981 700 627(89.6) 73 (10.4) (Sealy 1980a). This is the only Manitoba-banded Bullock's 4,434 199 197(99.0) 2 (1.0) "Baltimore" Oriole that has been recovered in winter Totals ,50,415 899 824(91.7) 7,5 (8.3) (Table 3). *"Baltimore"Oriole (Icterus galbula galbula); "Bullock's" Oriole (I. g. bullockii). Rogerset al. (1982)presented three criteriafor designating **An encounter is defined in North American Bird Banding Tech- niques, Vol. 1, 1977, appendix A-4, as an observationof a a speciesas a winter resident: (1) frequencyof repeats previouslybanded bird. Encountersoccur through hunting (recapturesduring the samewintering season), (2) the time or finding birds dead (recoveries),trapping (repeats, returns, lapse between repeats,and (3) recapturesof individuals retraps),or sightings by observers(not included in the pre- sent analysis). during subsequentyears, implying that an individual is ***Encounter rate: Baltimore, 1.52%; Bullock's, 4.49%; both more likely to be a return if it is a winter residentthan subspecies, 1.78%. if it is a transient. These authors considered 3 weeks to be an adequateinterval betweenrepeats for designating an individual a winter resident. The recovery in Guatemala of the Manitoba-banded oriole therefore does not constitute,by the criteria of Rogerset al. (1982), a record of a resident wintering bird. On the other hand, this individual probably was resident when and where it was recovered, although it is not known whether the wet and dry seasonsinfluence the areas this species choosesover the wintering period (e.g., Karr 1971, Mor- Table 2. Mist-net captures, repeats and returns, and ton 1980). The return of migrant passerinebirds to the sightingsof color-marked AHY "Baltimore" same locality in winter has been reported from Central Orioles during the late nestling and post- and South America (e.g., Schwartz 1963, Loftin 1977, breeding periods on the forested dune- Thurber and Villeda 1980, McNeil 1982, Rogers et al. ridge, Delta Marsh, Manitoba, 1976-1983. 1982) and the West Indies (Diamond and Smith 1973). Rogerset al. (1982) banded 8 Northern Orioles (of the MALES FEMALES "Baltimore"subspecies, D.T. Rogers,in litt. 4 January 1984) 7.DAY PERIODS SY ASY in Guatemala in March and April, 1979, but only one Jun 28-4 30* 64 143 repeated,3 daysafter it wasbanded, and nonewas recap- Jul 5-11 6 41 62 tured at the samelocality during the sameperiod in 1980. 12-18 3 10 17 Evidencefrom Honduras(Table 3) suggests,however, that 19-25 1 4 27 "Baltimore" Orioles do indeed return to the same locali- 26-1 0 14 13 ty in winter (see also Nickell 1968). One male banded Aug 2-8 0 15 11'* there in May, 1964, was recoveredin December of the 9-15 0 12 9 same year; 1 of 3 males banded between 13 and 20 16-22 0 5 3 December 1964 returnedthere the followingMarch, the 23-29 0 2 2 other two one year and about 18 monthslater, respective- 30-5 0 I 0 ly; one male banded in early December, 1966, repeated Sep 6-12 0 0 1'** the following March, and a male bandedin late March, * Includessingle SY males collected on 30 June and 5 July 1978. 1965, was recoveredthere about 6 years later. Observa- **Includes three mist-net mortalities. tions of "Baltimore" Orioles in Costa Rica and Panama ***AHY female (74-180909),banded on the dune-ridge study area suggestthat they are not only residenton their wintering on 16 July 1974, was recaptured on 9 September 1975 still on study area. When recaptured,its ninth primarywas about 90% groundsbut alsoterritorial (e.g.,Timken 1970, Leck 1974, grown. Schemske1975). Page14 NorthAmerican Bird Bander Vol. 10,No. 1 The singlerecovery of a Manitoba-bandedoriole on its Three orioles, banded during spring migration or the presumedwintering grounds obviously does not tell us breedingseason in Connecticut,Illinois and Ontario,also where the dune-ridgepopulation overwinters. It is not have beenrecovered in Guatemalain winter (7hble3).