Range Expansion of the House Sparrow Through Guatemala and El

RANGE EXPANSION

Rangeexpansion of the House Sparrow throughGuatemala and El Salvador

HouseSparrow (Passer domesticus). Photo/Allan D. Cruickshank/VIREO.

The hardy, adaptable Passer domesticus appears to be at home anywhere from Manitoba through Central America.

Walter A. Thurber

States;Robbins (1973) summarizes the it was nearly everywherein the States. studiedthe HouseSparrow (Passer spread and distribution in North By 1969, it had reached southern Can- NYONEdomesticus)WHOrecognizesHAS EVENitsCASUALLY capabil- America as of 1970. This specieswas ada and northern Mexico. ity for rapid range expansion.Bent introduced into eastern cities of the By comparison, the history of the (1958) provides the best documented United States in the 1850s and 1860s House Sparrowin South America is less account of the introduction and early and by 1886 it was broadly established detailed. It was introduced in widely spread of the species in the United east of the MississippiRiver. By 1910, separatedsites and few people kept rec-

Volume 40, Number 2 341 ordsof firstappearances Range expan- prevented further field work But what Atltlfin,Sololfi(1564 meters) Christmas sion has continued since Summers- we learnedgave tantalizing glimpses of Bird Counts at the lake show colony Smith (1963) first summarizedthe data the speciesin a new environment. growth:8 in 1974; 30 in 1975; 50 m from about 1960 on. The specieswas 1976;42 in 1977; 100 in 1978 (Holhn- introduced at Buenos Aires in 1870 rake 1975; Brose 1976-1979). Leahy (Boucherand Bedanoi 976), spreading SOURCES recordedthe specieson the Pacificslope rapidly throughout Argentina (Ulrog 1975 at Esquintla (347 meters); 1979 at 1959). It reachedUruguay in 1900, col- Many early recordsof House Spar- the nearby towns of Democracia and onizing it completely(Gore and Gepp rowsin Central America wereprovided Taxisco; 1979 at Mazatenango,Such•- 1978), and then moved up the Paraguay for this studyby knowledgeablebirders tepequez;he noted the speciesin 1978 River (Smith 1973) into Mato Grosso, who noted the species.Our own expe- in E1 Pet6nat Flores(115 meters)and Brazil, where it was reported in 1952 riencewith House Sparrows.in Guate- two nearby towns. (Sick 1959). Birds of the same origin mala were those of a traveling birder After the first sightingsin Guatemala went westward acrOssParaguay into visiting a wide range of localities;but, City in 1972, reports were frequent southern Bolivia, appearing in La Paz in E1 Salvador, weekendsfrom 1966 to Villeda(pers. comm.) noted the species m the 1950s(Summers-Smith 1963). A 1969 were spent mapping speciesdis- in severalparts of the city in 1974; it is transplantationto P•nm Arenas, Tierra tribution, and from 1969 through 1979 now widespread and common there del Fuego,in 1918, initiated a colony a major portion of time was spent in (pers. obs.). Villeda saw House Spar- that spread to Ushuaia at the southern the field. In 1977, along with 13 Sal- rows at Cabarias,Zacapa (280 meters), tip ofthe continent by 1957(Humphrey vadorans, an Organizedtown-by-town in August 1974, and learned that they et al. !970): In 1904,House Sparrows censusof E1Salvador's House Sparrows were new ardvals. In early 1976, we were liberatedin Santiago,Chile; they was made. In 1978 and 1979, follow- found them abundant at Cabarias and spreadover the entirecountry (Johnson ups were done with brief trips to check presentin nearby Zacapa. 1965), crossing into Peru in 1951 colony developmentand range expan- We believethat the invasion of Gua- (Koepke 1964), and proceededup the sion;other membersof the team con- temala began not long before 1970 coastto Lima where they were reported tinued to add information. Many sectionsof Guatemala were vis- in !953 (Summers-Smith1963). From 1977 through 1979, visitsto a ited for severalyears without seeingthe An introduction at Rio de Janeiro in fewnesting colonies continued for ad- species.House Sparrowswere not noted 1904, and another in Rio Grande do ditional data. The Christmas Bird duringthe 1960sby Land (1970) or by Sul in 1910, led to widespread coloni- Count (hereafter, CBCs) issues of Ibarra(per& comm.). In 1969,the range zation of southeasternBrazil, including American Birds from 1974 on include of P. domesticuswas not reported in the capital, Brazilia, where the species a site in Guatemala. The results of the the southernstates of Mexico (Robbins appearedin 1959(Smith 1973). For a CBCs clearly show the population 1973), except for an outlier at Tuxtla time it seemedthat the hot, humid cli- build-up through the early years fol- Gutierrez, Chiapas,where a small flock mateof the Amazon might be a barrier, lowing invasion. appearedin i950 (M. Alvarezdel Toro but Smith (1973) found a flourishing Prepared skins, skeletal and spirit 1950; in lift. 1977). colony at Maraba, Para. He suggested material for possiblefuture study of Range expansionthrough El Salva- that the birds ardved via the new high- phenotypicchanges has been deposited dor. Monroe (in litt. 1976) observedtwo way from Brazilia and that they might at the American Museum of Natural males at La Herradura, La Paz (5 me- continue along the Transamazon History. ters) January 7, 1972. Strauch (in hit Highway westward. 1974) saw "about a dozen" on the out- The demonstrated adaptability of skirtsof SanMiguel (100 meters) May House Sparrowsindicates that the spe- INVASION AND COLONIZATION 14-15, 1973. On July 22, 1973, we cieswill eventuallyinhabit most of the found a flourishingcolony. of 35_+birds Western Hemisphere. When we first Range expansion in Guatemala. and 11 active nests at San Marcos saw House Sparrows in western Gua- House Sparrowswere first recordedfor Lempa, Usulutfin (90 meters); local temala (Thurber 1972), we did not this country May 1, 1970, at Quezal- people had captured birds for saledur- doubt that their advance would con- tenango (2350 meters elevation), ing the precedingrainy seasonbetween tinue through Central America. This (Thurber 1972). On January 15, 1971, May and September1972. Hamel (tn presentedan opportunity to trace the Alden (in lift. 1977) observed10 at Chi- lift. 1976) sawa pair in the centralplaza progressof the speciesand studyits ad- chicastenango,Quich6 (1800 meters). of Usulutfin(100 meters)June 24, 1974, aptationsto new conditions.After some In 1972, Ewert (in litt. 1973) noted and others(pers. comm.) at La Um6n derailed study, the political situation House Sparrowsas follows: March 31, (5 meters), July 19-20, 1974. Alrey a pair in Guatemala City (1480 meters); (pers. comm.) found House Sparrows April 2, several at Chichicastenango; at SanFrancisco Gotera, Moraz•n (200 April 3, common at Quezaltenango. meters), in May 1975. From 1972 on, Leahy (in lift. 1978, The House Sparrowcensus of 1977, 1980) saw the speciesin "all towns of described below, showed the species anysize" in thewestern highlands and broadly but not uniformly distributed in many lowland towns, considering with major exceptionsin the highland them common to abundant. Leahy ob- areas.Certain early colonieshad dou- servedHouse Sparrowsin 1972 at Lake bledor tripled, and a fewhad multiphed

342 American B•rds, Summer 1986 Table 1. Growth of House Sparrow coloniesin El Salvadorfollowing first years reported. of the speciesacross the United States (Robbins 1973) and South America Locality First record Status in 1977 (Summers-Smith 1963). Caged birds, La Herradura, La Paz 2 (1972)• 10+_2 often miles from their origins,are com- San Miguel, San Miguel 12+_(1973) • 99 est., 3 colonies, 9 nests mon in Central American markets. Es- San Marcos Lempa, bridge capedor releasedbirds might form the Usulutfin 25-50 (1973) 11 nests 75 counted, 15 nests nucleus for a local colony. Perhapsthe Usulutfin,Usulut•n 2 (1974)• 250 est., 4 colonies, 62 tests colony at Tuxtla Gutierrez, Chiapas, La Unirn, La Unirn "some" (1974) 40 est., 2 colonies, 7 nests first noted in 1950, far south of the main San FranciscoGotera, Moraz•n "several" (1976) 22 est., 2 colonies, 1 nest wave, was founded by escapees.

• no effortmade to determineactual population. Results of the 1977 census. We sur- 2 heavdywooded conditions at La Herraduramade counts difficult. veyed 86 "municipios" of the 261 listed in the official registry of El Salvador (Fig. 1); thosenot visitedwere hamlets, into three or four colonies(Table 1). dor to Costa Rica, 600 kilometersin two most accessibleonly by 4-wheel drive There were unexpectedgaps along pos- years(275 miles/two years),and the av- vehicles. We found 35 colonies of sible invasion routes, some of which eragerate for all of CentralAmerica, House Sparrowsin 26 towns (Table 2). filled in during the following two years, whichmay range from 160kilometers/ The total counted for the country was notably at San Salvador(650 meters), year to 240 kilometers/year. Smith 499, with an estimated population of where by 1980, small bands were seen (1973) noted an advance in Brazil of 1100 birds. in severalparts of the city. 800 kilometers in six years (500 miles/ ß The total of our counts underesti- We doubt that House Sparrows were six years) from Brazilia to Maraba. mates the actual population because' presentin El Salvador much before the Robbins estimateda radial spreadof 1) not all townswere visited;2) we may P. domesticus from coastal cities of firstsightings. During the preceding five have missed colonies in the larger yearswe had been mappingspecies dis- North America at about 8 kilometers/ towns; 3) we did not look for colonies tnbutionsthroughout the regionswhere year (5 miles/year) during the early outside town limits; 4) some colonies the first colonies were found. Note also years.Judging from his maps, the rate were visited during hot midday hours the pattern for both Guatemala and El did not changegreatly during the spread when birds are lessactive; 5) foraging Salvador, no records until suddenly a of the speciesacross North America and birds may have been outside their col- spateof sightingsfor a fairly large geo- southwardthrough Mexico. By com- onies;6) incubatingand broodingbirds graphic area, as though the birds had parison, the rate 'through Central may have been missed.We returned to movedin like a wave of migrants. America has been spectacular. four colonies for comparison counts, Rangeexpansion beyond El Salvador. our estimateswere about the same, but Topography'sinfluence on range ex- Stiles (in litt. 1977) reported that in actual leisurely counts were higher pansion. In North America, House Costa Rica, House Sparrowswere pres- Taking into considerationthese factors, Sparrowsdispersed radially from sites ent "in flocks" on the Central Plateau we believe that the population of the of introduction, merging in a broad in February-March 1974, and were areas studied was no fewer than the es- front acrossthe continent relatively un- well-established in Guanacaste Province timate of 1100 birds, and was 1500+ hampereduntil they reachedthe Rocky in early 1975; by 1977, the specieswas for the entire country. Mountains. But in Chiapas,Guatemala, presentin most major cities and towns and El Salvador, the birds were chan- of thenorthwestern and centralPartsof Distribution in El Salvador in 1977. neled between the Pacific Ocean and the country but had not arrived on the The eastern lowlands, sea level up to Caribbean slope. inland mountains;the front was only 300 meters, provided P. domesticus 60-125 kilometers wide. Robbins The late E. Eisenmann (in litt. 1980) with conditions satisfactory for rapid (1973) estimateda radial spreadfrom summarized recent records for Panama. and widespreadcolonization; nearly all coastal 'cities as 160 kilometers in 15 The earliestrecord is in 1975, in David, colonies, including the largest, were years;the semicirculararea thus colo- Chlnqul. The specieswas also seenin found there. We had no reports of col- nizedwas about 40,000 km 2, a rateof Panama City in 1979. onies in the northern highlands. The about 2500 km2/year. In Central westernhalf of the country, topograph- Rate of range expansion.The first America, assuminga frontal w•idthof ically diverse,was spottily colonized at records for House Sparrows in Guate- 100 kilometers and a minimum speed four well-separated sites; House Spar- mala and El Salvador,respectively, span of 90 km/year, the rate of colonization rows were unaccountablyabsent from an interval of lessthan two yearsat sites wouldbe about 9000 km2/year Or more. some360 kilometers(220 miles) apart. Another factor to be considered as Thus the rateof advancemay havebeen affectingthe rate of expansionis the 180 kilometers/year(110 miles/year); density of suitable colonization sites. less if the birds arrived in Guatemala Generallythe densityof sitesin Central before 1970. If the birds were in Gua- America is high. temala in 1968, the rate would have Introduction, deliberate or acciden- been about 90 kilometers/year (55 tal, of HouseSparrows into newareas tories/year).The higher rate is more is another factor. Deliberate introduc- consistent with the rate from E1 Salva- tionwas important in theearly spiead

Volume40, Number2 343 344 AmericanB•rds, Summer 1986 Table 2. Populationsand nestsof House Sparrowsrecorded during the 1977 censusof this b•rds and one nest on the eastern edge speciesin 86 municipiosof El Salvador. of the city. In 1978, we sawa small flock Departmentand municipio Population Nestsfound but no nests. Seemingly the original colony expandeduntil the carryingca- La Uni6n, La Uni6n 16 (40)* 7 pacity of the plaza was reached.At least Santa Rosa de Lima 6 (15) 1 one pair left and found suitable condi- San Miguel, San Miguel 36 (100) 9 tions in the cemetery.Excess birds from Chinameca 2 (2) 0 this and/or the mother colonycolonized Moraz•n, Jocoro 10 (25) 5 San FranciscoGotera 12 (20) 1 adjoining sites. Multiple colonies in Usulutfin,Usulut•n 152 (220) 62 other towns may have been established Puerto Parada 6 (20) 0 in the sameway. Puerto Triunfo 7 (15) 0 Jiquilisco 31 (110) 18 Changes in El Salvador after 1977. San Marcos Lempa 75 (110) 25 Scattered reports show that House Tierra Blanca 8 (10) 0 Jucuapa 9 (20) 0 Sparrows continued to multiply and PuenteCuscatl•n 1 (2) 0 colonizenew areas.Most reportsare for La Paz, Zacatecoluca -- (26) 7 San Salvador for which we had no rec- San Juan Nonualco 8 (25) 1 ordsthrough 1977. In December 1978, San Rafael Obrajuelo 6 (15) 0 Andino (pers. comm.) reported House SantiagoNonualco -- (25) 0 Sparrowsin a small plaza near the city La Herradura 10 0 Cuscatl•n, Cojutepeque 4 (10) 0 center; Villeda (pets. comm.) verified Perulapia 14 (25) 1 the report January 29, 1979, finding San Salvador,Ilopango 25 (60) 0 eightbirds in this barrenand busyplaza. Santa Ana, Metapart 15 (25) 0 Villeda also observeda pair in the east- Chalchuapa 12 (15) 2 ern part of the city May 24, 1979. In Sonsonate,Izalco 14 (20) 0 December 1979, Wall (pers. comm.) Armenia 20 (40) 1 saw 4-5 birds at the Ilopango airport, * Numbersoutside parentheses are actualcounts; numbers in parenthesesare estimates. and in January 1980, 10-12 in Colonia SanCrist6bal, a suburbnear the airport. On August 3, 1979, we saw 5-10 the coastal strip and inland hills. Su- consideringthe size of the wild bird HouseSparrows at Usulutfinbut found perficialacquaintance with population trade, but rcquiresthe almost simulta- no nests. centersdoes not suggestdifferences that neousliberation of captivebirds in sev- We traveledthe PanamericanHigh- explmnsuch discontinuous distribution. eral well-separated places. way from San Salvador to the Guate- A third hypothesis proposes that malan border February 29, 1979. At Invasion patterns in El Salvador. House Sparrow coloniesbuilt up to in- Chalchuapa,where 12-15 birdsand one Dunng the 1977 census we tried to supportable levels. Excess birds, espe- nest were seen June 25, 1977, we now •dentify a town-by-town invasion route cially immatures which show little at- saw 50 birds (estimated) and 10 nests from Guatemala. There arc three rea- tachment to natal sites (North 1973), At Ahuachapfin,where no birds were sonableroutes: 1) along the coastfrom tended to disperseand were carded seenin 1977, we saw five birds but no Esqmntlathrough a regionof large ha- away by the long-lasting,violent wind nests. At Santa Ana, we saw one male ciendas and few towns; 2) along the storms that frequently lash the region. and heard one other bird in the central Panamerican Highway with its many Occasionallya pair arrived at a favor- plaza, but found none in other parts of townsfrom Guatemala City throughthe able site far from the source. the city. western hill region; 3) from Zacapa Habitats colonized.Thus far, records through a passin the northern cordil- Colony growth. Table 1 prcsentsdata of P. domesticus in Guatemala and E1 lera. The census teams checked the on the growth of the earliest colonies. Salvador are confined to populated towns along these routes with special The earliestdata was obtained in pass- places.Alvarez del Toro (in litt. 1977) care, some were double checked. We ing except at San Marcos Lempa where emphasized the same for Chiapas, we spent morc time on successivedays. found no House Sparrowsin Acajutla, Mexico. Within towns and cities most Sonsonate or La Libertad along the A pattern of colonygrowth and disper- colonies have been found in the central coastal route. We found one small col- sion can be inferred from the data for plazas. SpanishAmerican towns were ony at Chalchuapaalong the Panamer- Usulutfin. In June 1974, Hamel ob- ican Highway. We found a colony at serveda pair of House Sparrowsin the Metapfin on the route from Zacapa, but central plaza. In May 1977, the census •t •s unlikely that this wasthe sourceof team counted 52 birds (100 estimated) the eastern populations unless House and 29 active nests in the plaza. We Sparrows had been present in the Za- found another colony at 84 birds (120 capa rcgionlong beforethe 1974 rcport. estimated)and 32 nestsin a cemetery An hypothesisthat explains the dis- at the westernedge of the city. Two ki- continuous colonization suggeststhat lometers west of the city we found a the earliest colonies derived from cap- colony of 16 birds and one nest. A ave birds. This is not unreasonable month later we found a colony of 6-8

Volume40, Number 2 345 lind out on a rectangulargrid with four set, rough twigs firmly anchor the by their supportswere globular, 25 to or more blocks left at the center for a loosely compacted nests of House 35 centimeters in diameter. plaza. Buildingsoutside the plaza abut- Sparrows. Palms probably serve as ted the streetsclosely, leaving litfie space nesting sites more often than records Nestingphenology. Figure 2 prowdes for grassand trees. The central plaza indicate; nestsare rarely visible in the a monthly summary of data on repro- usuallybecame a smallpark, with either elevated, compact crowns although ductive activity of House Sparrows•n just a few palmsor fully developedwith nestingcan be inferredwhen birds bring E1 Salvador. Visits to the lowlands were ornamental plantingsand crisscrossing nesting materials and food. Villeda infrequent in Decemberand January. walks. As a town grew, secondaryplazas (pers.comm.) saw extensive nesting ac- Data then are scant.Approximate egg- might be left by churches,and open tivity in a groveof CoconutPalms (Co- laying dateswere obtainedby extrapo- spaceswere provided at schools,clubs cosnucifera) at Cabarias,Guatemala. Of lation, assumingthat sparrow devel- and cemeteries. One feature common man-made structures, churches with opment in E1 Salvador proceedsas •n to all, and this is important to House clock and bell towers were most notable: New York State: 12 daysfor incubation Sparrows,was the presenceof benches nests were built on cross members be- (Weaver (1943); 15 days as nesthngs, where people congregateand eat at all neath the roofs; in niches in the walls and 4-6 weeksbetween fledging and full hours.Typically discards are thrown on of old churches; under traditional molt (Weaver 1942). The data for the ground. House Sparrows have an curved roofing tiles that leave arched Chalchuapa(600 meterselevation) are unfailing supplyof food, though rarely spacesat the eaves;within archedspaces separated from data obtained near sea plentiful. The scavengedfood is sup- between corrugated asbestos roofing level although there is no firm evidence plemented with seeds and insects sheets and the side walls. Nests were also that altitude affectsbreeding schedules gleanedfrom grassyand/or weedyplots. found on roof trusses and beams and Meteorological Servicetables show that Within the plazas House Sparrows in cavitiesin walls of buildings.A few the rainy seasonin the lowlandsbegins face little competitionexcept from the were found in natural cavities and slightlylater, producesmore rain, and ubiquitousstarving dogs ready to snatch woodpecker holes in tree trunks. Han- lasts a month longer than at Chal- up any crumb, and in someplazas from gers supportingthe cablesof the sus- chuapa,and that averagemonthly tem- a few Rock Doves(Columba livia). Pre- pension bridge at San Marcos Lempa peraturesare about 6 ø higher. dation is limited, mostly to boys with provided sitesfor many nests. Molting juveniles of May 27, prob- shngshots.Nesting sites are plentiful: Of the 60+_ nests examined, most ably hatched from eggslaid about the palms, Casuarinas( Casuarina equise- were loosely compacted masses of beginning of March. Juveniles seen ttfolia), bell and clock towers,niches in strawswith a few fine twigs, occasional April 26, indicatednesting as early as church walls. But strictly residential plant fibers and bits of string. The late February. Non-molting juveniles areas have little to offer House Spar- chamberswithin werealways lined with from October 26, indicated nesting•n rOWS. chicken feathers. Nests not constrained September,possibly earlier. A sexually Colony sitesoutside the plazashave s•milar features.The cemetery at Usu- LOWLANDS lutfin has a row of Casuarinas with benches;Usulutfin servessnacks in its J F M A M d d I A S O N D patio beneathCasuarinas; San Marcos Lempa has a bridge adjacent to a strip of roadside markets where transients refresh themselves.The port towns of La Herradura, Puerto Parada, and PuertoTriunfo have no plazasbut people congregateand eat at the docksto wait for the tides.

ADAPTATIONS IN CHALCHUAPA REPRODUCTIVE BEHAVIOR

Nest sites and nests. Most of the nests seenwere in Casuarinatrees, the close-

dry season wet season dry Figure 2. Phenologyof reproductiveactivities of Passerdomesticus in El Salvador.'low/ands, 0-100 meterselevation,' Chalchuapa, 600 meterselevation 1) nestbuilding and/or copulatton, 2) eggsand/or incubation; 3) nestlingsand/or food delivery at nest,'4) juveniles and/or Jkedtng offiedglings,' 5) juvenilesin molt.Bars: observed activities,' stars: activities inferred by extrap- olationsJkom dates of observedactivities.

346 AmericanBirds, Summer 1986 activefemale with eggsready to lay was Table 3. Numbersof eggsand/or nestlingsin 22 House Sparrownests found in the lowlands examined October 26; she might have of El Salvador 1977. nestedin early November and fed nest- Number/nest 1 2 3 lingsin mid-November, possiblylater. On May 27, we examinedtwo sex- Eggs 2 0 9 t ually activefemales in juvenal plumage, Nestlings 0 9 22 one with an imcompletelyossified skull includes1 nestwith 2 eggsand I hatchling, (StageB, NorthAmerican Bird Banding nestlingswere 1-3 daysold. Manual, 1977). Extrapolation to their hatchingdates is complicatedbecause cussion was a female with one ovum in were extremely fat, suggestingadequate nestinginterrupts or defersmolting in her oviduct and two almost ready to suppliesof food for eggproduction. somespecies, and possiblyaffects skull enter, and another with three ova of ossification.Assuming no interruptions, three, two plus, and two millimetersre- Nestlingsand nestlingsuccess. Table these females could have come from spectively. 4 givesdata on nine nestlingsfrom four eggslaid betweenFebruary and April; The limited evidence suggesteda nests,plus two siblingsthat were pho- otherwisethey might have been six clutch size of three for P. domesticus in tographedbut not measured,and a trio months older, hatched from eggslaid El Salvador, smaller than the 4-5 re- of nestlingsthat were hurriedlyexam- between November and February. ported for more northern latitudes. ined. These last showed differences in Feeding of nestlings was noted at Latitude seems to be a constraint on sizeand developmentsimilar to the first ChalchuapaJune 25; nestbuilding, in- clutch size in many spedes (Skutch trio in the table. cubation, and feeding of nestlingsin 1976). Cody (1971) plotted clutch size The smallestof three siblingsin each February.The nestingseason there thus vs latitude for genera present in both of two nests was about one-half the size extendsfrom January at least through temperate and tropical zones;interpo- of its nestmates and seemedvery weak. June. lation for 13øN on his curves predicts Theserunts (barely able to sit up) could In Guatemala, Viileda (pers. comm.) a dutch sizeof two plus for E1Salvador. not competevigorously with their sib- saw House Sparrowscarrying nesting Murphy (1978) plotted dutch size of lings.Incubation might have begunbe- materials and food at Cabarias in mid- House Sparrows vs latitude between fore the third eggswere laid. Murphy June and the beginning of November. 35øN and 51øN; extrapolationfor 13øN (1978) noted 26 casesof incubationbe- We observednest building May l, at on his plot predictsa clutch size of 3.5 fore completion of dutches, although Quezaltenango. for E1 Salvador. he believedthat the initial disadvantage In Costa Rica, Fleischer(1982) saw In Costa Rica, Fleischer (1982) ob- of late hatchingwas compensatedfor HouseSparrows feeding fledglings Feb- tained data on seven nests: one with one by other factors. However, in the in- ruary 17; extrapolationputs egg-laying egg(possibly an incompletedutch); one stancesdescribed for El Salvador, the datesin mid-Januaryor earlier.He cites with one nestlingabout to fledge;three runtsseem to be increasinglydisadvan- a personal communication from Stiles with two eggs(one nestjudged with a taged, perhapsbecause the diet was in- that House Sparrowsnest in San Jos6 complete clutch becausenestlings were adequatein quantity and/or quality. through October and may nest year- being fed 10 days later); one with two The nestlingsin four broods of two round. nestlings(ages not given);one with three were estimated at about 2, 4, 8+, and This evidence suggestsyear-round eggs.He alsofound a "dump" nestwith 8+ daysold, respectively.In each duo, breedingof P. domesticusin Central 10 eggsand an incubatingfemale, a rar- one nestlingwas somewhat smaller and America, which is not especiallysur- ity. Assumingall clutchescomplete and lessdeveloped than its sibling,but ob- prisingif we considerthat nestlingsare ignoring the dump nest, Fleischer's viouslynot enoughto prevent survival. reportedevery month in North Amer- nests averageslightly fewer than two Our limited data suggestthat the dif- ica, includingwinter months (Cottam eggs/nest,an absoluteminimum that ferencescontinue through the nestling 1929; Snow 1955; Wessels1976). But does not consider possibleincomplete stageand that the initial disadvantage in North America, the cycle of repro- clutchesor nestling fatalities. Extrapo- is not compensated for. duction of P. domesticusis generally lation from Murphy's (1978) plot pre- linked with the photoperiod (Burger dicts a clutch size of 3.3 for Costa Rica. Age at first breeding.A femalein ju- 1949). Day length in Central America It has been proposedthat latitude venalplumage, not molting,on May 18, changesso slightly that it is possiblethat operates on dutch size through day had an incompletelyossified skull with the reproductivecycle is free-running. length. Lack suggeststhat shorterday- a large "window" on each side; this Only color-bandingstudies can answer light hours (11-13 in El Salvador, 15+ suggestedan age of six months or less the many intriguing questionsraised. during the breeding seasonin North Clutch size.Table 3 givesdata for 22 America), reducesthe time availablefor nests.Clutches with one eggmay have obtaining adequate food for large been incomplete.A nestwith two eggs clutches.Ashmole (1963) proposesthat and a hatchling is included with eight in higher latitudesthere are flushesof nestshaving three eggs each. Two nests availablefood during the summers.The each containing very young nestlings presence of runts and probable runt wereprobable 3-egg dutches. Nine nests mortalityin El Salvadorsuggest insuf- with two older nestlingseach may have ficient food or insufficient time for food lostthird nestlings.Relevant to this dis- gathering,but three prelayingfemales

Volume 40, Number 2 347 Table 4. Data on 14 nestlingsfrom 6 nests of Passerdomesticus, El Salvador, 1977. Ages beneficial though not entirely so. Cer- are estimated using Weaver (1942). tainly birds that can colonize Death Nest No. Weight (g) Length (mm) Ulna or wing (mm) Age (days) Valley, California, and Churchall, Manitoba, would find nothing insup- 9 62 11 4+ portable in the temperaturesof Central #77-5-18D 61/4 60 10 4 America. Especially beneficial was the 4 50 6 2+ liberation from heavy winter mortahty

63/4 63 9 2+ Whichsometimes takes up to 50%of a #77-5-18E 41/2 53 6 1-2 population, especially among young birds(Will 1973). The effectof long dry 22 92 33 8+ seasons is undetermined. A House #77-5 - 18C 181/4 80 26 7+ Sparrowdrinks up to 30% of its weight

201/• 85 32 8+ daily, more if heat stressed(Bartholo- #77-5-18B 18 80 28 7+ mew and Cade 1963). In most of E1Sal- vador and much of Guatemala there •s #77-4-26B ------4+ fittle free water in rural areas from m•d- November to mid-April; all but the largeststreams go dry midway through

#77-4-26C ------4- the period. This may be a factor that ------2+ limits House Sparrowsto towns where free water is found. Possiblythe most adversefactor hm- (Nero 1951) if ossificationproceeds at (Davis and Davis 1954); three males,in iting the spreadof this specieshas been the samerate in the tropicsas in higher June, July, and August, respectively, the presenceof already well-established latitudes. This female had no incuba- skullsunossified to one-quarterossified, species.Conditions in Central America tion patch and was extremely fat. She juvenal plumagewith a few adult feath- have long been relatively stable;native was nearly ready to lay; one ovum was ers, bills black to very dark brown birdshave partitionedthe resourcesand 12 millimeters in diameter and almost (Davis 1953). Early breeding has been occupiedthe niches. These native birds free, two others, 8 millimeters and 7 noted in other species(Miller 1959a; are K-selectedand so make exceptional millimeters, respectively, were almost Miller 1959b; Immelman 1971; John- competitors in the environments to free.A femaleon May 17, had an unos- son (1962). which they are adapted(Meyers 1977) s•fied skull, possibly less than four However, the native birds rarely •n- months old, with an active ovary with vadedthe compact,comparatively bar- ova 3, 2+ and 2 millimeters, respec- DISCUSSION ren towns of Spanishdesign. There the tively. Shewas very fat and not molting, House Sparrows,already adapted to hve and still in juvenal plumage.We believe The rapid expansionof P. domesticus close to man, found the plazas and that both birdswere nestingor about to through Central America appearsto be parks almost free of competitors.Food, do so. a simple caseof an r-selectedspecies in- thoughinferior in quality and quantity, We find no referenceto proven nest- vading a region where K-selection is was dependable. Nest sites were plen- mg by very young House Sparrows as appropriate (Mac Arthur and Wilson tiful. Native predatorswere too tim•d confirmed by color banding studies; to live in the towns. 1967). In simpler but lessconcise lan- most such studies have been carded out guage: a species of northern Europe And so the House Sparrows flour- m temperate zoneswhere winter inter- adapted for high reproductive potential ishedin towns. When they tried to d•s- posesa hiatus in the sexual cycle. A few in orderto recuperatequickly from cat- perseinto open country they met w•th •ndividuals with active gonads but in astrophicwinter losses,has moved into the full force of competition and w•th juvenal plumageand with incompletely a region where conditions are favorable predators for which they had no de- ossifiedskulls, have been reported from and relatively stable; with high fecun- fense. Adaptable as they are, House the mild climate of southern California: dity and low mortality an excessof Sparrowshave not yet beenable to find, two females, in March and April, re- young is produced, more than can be open, and exploit niches outside the spectively,skulls partly ossified,the first accommodatedat any one site, and the towns in Guatemala and E1 Salvador •n a low stageof sexual development, excessis forced to emigrate. However, This explains the small absolute the second in full breeding condition the matter is not that simple. numbers of House Sparrowsin E1 Sal- The full effect of latitude change is vador where we estimated fewer than yet to be discovered.Our data and that 2000 in 1977. This number is trivial of Fleischerin Costa Rica suggestthat compared with 15,000 breeding b•rds clutch size is affected,but this may be in McLeansboro, Illinois (Will 1973), an indirecteffect, possibly owing to dif- 20,000 birds feedingin one squaremde ferencesin quality and availability of near Stillwater, Oklahoma (North food, or to releasefrom photoperiodic 1973), and 330 pairs/100 acresof sub- and/or seasonal control, permitting urban Pinellas County, Florida (Wool- more but smallerclutches/year. fenden and Rohwer 1969). However, The changein climate was probably North American House Sparrows are

348 American B•rds,Summer 1986 not confinedto a few hundred meterse Victor Marin plannedthe itineraries HOLLINRAKE, J (compiler) 1975 The of a verycompact town; they can forage for the 1977 census teams. Amanda seventy-fifth Audubon Christmas B•rd Count: SantiagoAtitlfin, Sololfi,Guate- widely on lawns, gardens, livestock Villeda helped organize the census mala. Am. Birds 29:597. feeding lots, grainfields,and at grain teams and also accompanied me on HUMPHREY, P. $., D. BRIDGE, P. W elevators and feed stores. House Spar- some of the follow-up trips. The census REYNOLDS, and R. T. PETERSON rows of Central America do not have teamsincluded: Mafia Elena de fi, brego, 1970. Birds of Isla Grande (Tierra del these resources. Antonio Argumedo,Ana Miriam Car- Fuego). Preliminary $mithsonian Man- Paradoxically,the factorsthat limit rillo, Letty F. de Escalante,Carlos Hi- ual, Washington, D.C. population growth may have been re- dalgo, Victor Manuel Marin, Rosa IMMELMANN, K. 1971. Ecologicalaspects of periodicreproduction. Pp. 341-389 m sponsiblefor the rapid rangeextension Maria de Marin, Miriam de Peraza, D. $. Farner and J. R. King, eds.Avian of the species.Consider the situation in ThomasPullen, Carlos Mauricio Ro- Biology,vol. 1. Academic Press,N.Y which a pair of House Sparrowsmakes sales, Oscar Dorindo Santos, Amanda JOHNSON, A. W. 1965. The birds of Chile its way into a suitabletown plaza.Their Villeda C. The Instituto de Turismo and and adjacent regions of Argentina, Bo- reproductiverate is high,their mortality the Central American Research Station livia, and Peril. Platt, BuenosAires, Ar- rate low; they increasegeometrically. of the United States Public Health Ser- gentina. JOHNSON, R. F. 1962. Precocioussexual vice loaned vehicles. Within a fewgenerations the colonywill competence in the Ground Dove. Auk have reachedthe carrying capacity of 79:269-270. LITERATURE CITED the site. There are few or no outside KOEPCKE, M. 1964. Las aves del depar- sources of food for additional birds. •LVAREZ del TORO, M. 1950.The En- tamento de Lima. Talleres Grfifica Mor- Another generationresults in an excess. glishSparrow in Chiapas.Condor 52:166. som, Lima, Perfl. Some of the immatures leave without ASHMOLE, N. P. 1963. The regulationof LACK, D. 1968. Ecologicaladaptations for breedingin birds. Methuen, London. aim or direction, perhapsbeing borne numbers of tropical oceanic birds. Ibis 103b:458-473. MacARTHUR, R. H., and E. O. WILSON on the strong north winds that fre- BARTHOLOMEW, G. A., and T. J. CADE. 1967.The theoryof islandbiogeography quently occur. They wander, many 1963. The water economyof land birds. Monog. in PopulationBiol. 1. Princeton succumb, some make their way into Auk 80:504-539. Univ. Press.Princeton, N.J. another town which may be far from BENT, A. C. 1958. Life historiesof North MEYERS, N. 1977. Garden of Eden to w•ed the mother colony. Thus the rapid ad- American blackbirds, orioles, tanagers, patch: the earth'svanishing genetic her- vance and saltatory progression. and their allies. U.S. Nat. Mus. Bull. 211. 'itage. National Resources Defense Council Newsletter 6 ( 1) 1-15. This amazingly adaptable species BROSE, M. (compiler). 1976. The seventy- sixth Audubon Christmas Bird Count: MURPHY, E. C. 1978. Breedingecology of may find waysto invade the rural areas, Cerro de Oro, Guatemala.Am. Birds 30: House Sparrows:spatial variation. Con- repeatingits North American history, 626. dor 80:180-193. but by means of entirely different ad- __.. 1977. The seventy-seventhAudubon NERO, R. W. 1951. Pattern and rate of cra- aptations. The species will probably Christmas Bird Count: Cerro de Oro, nial "ossification"in the House Sparrow continueto makeadaptations to the Guatemala. Am. Birds 31:898-899. Wilson Bull. 63:84-88. NORTH, C. A. 1973. Movement patterns chmite, photoperiod,latitude, compet- --. 1978. The seventy-eighthAudubon Christmas Bird Count: Cerro de Oro, of the House Sparrow in Oklahoma. Pp itors,predators, and diseases. Summers- Guatemala. Am. Birds 32:903. 79-91 in Ornithol. Monogr. 14. Smith (1963) consideredthat P. do- __.. 1979. The seventy-ninth Audubon ROBBINS, C. S. 1973. Introduction, spread, mesticuswas of tropical origin and that Christmas Bird Count: Cerro de Oro, and present abundance of the House it took some of its tropical adaptations Guatemala. Am. Birds 33:681. Sparrow in North America. Pp. 3-9 tn with it when it spread into northern BOUCHER, E. H., and P. E. BEDANO. Ornithol. Monogr. 14. Europe. It will be interestingto learn if 1976. Bird damageproblems in Argen- SICK, H. 1959.A invas•ode Amtrica Latina tina. Intern. studieson sparrows,9:14. pelo pardal (Passer domesticus).Boll any of its tropical heritage will assert Mus. Nacional Brazil. 207:1-31. Itself now that it has reinvaried the BURGER, J. W. 1949. A review of experi- mental investigationson seasonalrepro- SKUTCH, A. F. 1976. Parent birds and their tropics.We have been presentedwith a duction in birds. Wilson Bull. 61:211- young.Univ. TexasPress, Austin, Texas natural experiment which, if we hurry, 230. SMITH, N.J. H. 1973. House Sparrows we can useto test many of the theories COTTAM, C. 1929. The fecundity of the (Passer domesticus) in the Amazon Condor 75:242-243. and models that have been devised to English Sparrow in Utah. Wilson Bull. SNOW, D. W. 1955. The abnormal breeding explain someof the adaptationsof birds. 43:193-194. CODY, M. L. 1971. Ecologicalaspects of of birds in the winter 1953-1954. Brtt reproduction.Pp. 461-512 in D. S. Far- Birds 48:120-126. ACKNOWLEDGMENTS ner and J. R. King, eds. Avian Biology, SUMMERS-SMITH, J. D. 1963. The House vol. 1, Academic Press,N.Y. Sparrow. Collins, London. THURBER, W. A. 1972. House Sparrows I thank the followingpeople who, by DAVIS, J. 1953. Precocioussexual development in the juvenal English Sparrow. in Guatemala. Auk 89:200. letter or in person,helped me document Condor 55:117-120. the early stagesof the range extension and B. $. DAVIS. 1954. The annual go- of Passer domesticusthrough Central nad and thyroid cycles of the English America: P. Alden, D. Ewert, C. Leahy, Sparrow in southern California. Condor A Villeda, J. Ibarra, B. Monroe, Jr., 56:328-345. J. Strauch, Jr., P. Hamel, M. Avery, FLEISCHER, R. C. 1982. Clutch size in Costa Rican House Sparrows. J. Field F. G. Stiles, S. Andino, D. Wall. Victor Ornithol. 53:280-281. Hellebuyckassisted during my studies GORE, M. E. J., andA. R. M. GEPP. 1978. of the colonies at Usulutfin and San Las avesdel Uruguay.Mosea Hnos., Marcos Lempa. Montevideo, Uruguay.

Volume40, Number2 349 ULROG, C. C. 1959. Las aves argentinas. __. 1943. Reproduction in English Spar- WOOLFENDEN, G. E., and S. A. ROH- InstitutoMiguel Lille, Tecumfin,Argen- rows. Auk 60:62-74. WER. 1969. Breedingbirds in a Florida tina. suburb. Florida State Mus. Bull. 13. U.S. FISH and WILDLIFE SERVICE. 1977. WESSELS, T. 1976. Connecticut House Sparrowsnesting in December.Auk 93: Ageingand sexing,North American Bird 837. Banding Manual, vol. 2. Washington, D.C. WILL, R. L. 1973. Breedingsuccess. num- WEAVER, R. L. 1942. Growth and devel- bers, and movements of House Sparrows --Cornell UniversityLaboratory of opment of English Sparrows. Wilson at McLeansboro, Illinois. Pp. 60-78 in Ornithology,159 SapsuckerWoods Bull. 54:183-191. Ornithol. Monogr. 14. Road, Ithaca, New York 14850

NorthernHawk-Owl (Surnia ulula). Illustration/James Coe.

350 American Birds, Summer 1986 i

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Black-billedMagpies (Pica pica). Illustration[James Lish

Volume40, Number 2 351