NOTES BREEDING BIRDS OF ESTEROS TOBARI AND SAN JOS, SOUTHERNSONORA EDUARDO PALACIOS and ERIC MELLINK, Centro de Investigaci6nCientifica y Educaci6nSuperior de Ensenada,Apdo. Postal2732, Ensenada,Baja California, Mexicoor P.O. Box 434844, San Diego, California92143 Althoughthe ornithofaunaof Sonora has been studiedsince, at least,the 19th century(van Rossem 1945), it is stillrather poorly known. This is particularlytrue for its southerncoastal area. Van Rossemand Hachisuka(1937) providedan extensive list of water birdsfrom EsteroT6bari but found little evidenceof local breedingfor mostspecies. In 1971 and 1972, Knoderet al. (1980) madeaerial surveys of water birdsand wetlandsalong the coastsof BajaCalifornia and the westcoast of mainland Mexico, from the delta of the Rio Coloradoto San Blas,Nayatit, but did not include EsteroT6bari as one of their intensivelysurveyed sites. Here we report on the breedingbirds that we recordedon a trip to esterosT6bati (includingIsla Huivulai) and San Jos• on 14 May 1994 (Figure1). In EsteroT6bari, we surveyedthe north and south mouths of the bay, two isletsoutside the north mouth, and two herontieson the southeastand northwestsides of Isla Huivulai. San Jos• is a smallfishermen's town 8 km northwestof the north mouth of EsteroT6bari, with an esteroand a largesaltflat nearby, both of whichwe surveyed.We visitedalso an abandonedshrimp farm at the north end of EsteroT6bari. The main purposeof our trip wasto searchfor LeastTern breedingcolonies. Great Blue Heron (Ardea herodias). A heronry in NE Isla Huivulaicontained eightnests, one with two half-grownchicks. On the westcoast of mainlandM•xico, Great Blue Herons breed from the delta of the Rio Colorado (Palaciosand Mellink 1993) south to, at least, San Bias, Nayarit (Knoderet al. 1980). Gtiffing Bancroft (unpublishedfield notes) had found this species as a breederat EsteroT6bari in 1930, and van Rossemand Hachisuka(1937) collecteda specimenin breedingcondition from there. Great Egret(Casmerodius albus). Two heronriesin SE and NE Huivulaihad about 15 pairs with nestseach. Van Rossemand Hachisuka(1937) had recordedthis speciesas a breederfrom the area. SnowyEgret (Egretta thula). There were 20 pairsin the SE heronryand about the same numberin the NE heronryon Isla Huivulai.The Snowy Egret is reportedas occurtingalong the Pacificcoast of Mexicofrom PuertoPefiasco south to the Istmo de Tehuantepec(Knoder et al. 1980) and beinga residentfrom Guaymassouth (van Rossem1945), but no previousbreeding records exist for southernSonora. Little Blue Heron (Egretta caerulea).We found three pairs with nestsin each heronryon IslaHuivulai. This speciesis knownto occurfrom PuntaSargento south to the lstmode Tehuantepec(Knoder et al. 1980) and to be a summerresident of the mangroveassociation of southernSonora (van Rossem1945), but no particular breedinglocations had beenpublished. TricoloredHeron (Egretta tricolor).We saw five adultsfeeding on the mudflatin front of the heronryin NE IslaHuivulai; we presumenesting. Like previousspecies, thisheron has been noted from Guaymassouth to Tehuantepec(Knoder et al. 1980) and to be a residentof coastallagoons in southernSonora (van Rossem1945), but no specificbreeding locations had been provided. Western Birds 26:99-103, 1995 99 NOTES ReddishEgret (Egretta rufescens).We found three pairs with nests in each heronryon Isla Huivulai.This speciesranges from PuertoPefiasco to Tapachula, Chiapas(Knoder et al. 1980). Bancroft(unpublished field notes) found this species breeding at Estero T6bari, and van Rossem and Hachisuka (1937) collecteda specimenin breedingcondition there. CattleEgret (Bubulcus ibis). About 100 pairswere nesting in eachheronry of lsla Huivulai.This is the secondbreeding record for Sonoraof thisstill-expanding species (see Mellink and Palacios1993). Green Heron (Butoriclesvirescens). We found one pair on a nest in the SE heronry,and five pairswith nestsin the NE heronry.This secretivespecies, which is often overlookedand underestimated,was collectedin breedingcondition at Estero T6bari by van Rossemand Hachisuka(1937). Black-crownedNight-Heron (Blycti½orax nycticorax). We foundthree pairsnest- ing in the SE heronryand severalindividuals, with no evidenceof nesting,in the NE heronry.There were one adultand one immaturein nearbyagricultural drains. This speciesis often overlooked,even from the ground.Therefore, very likelythere were more individualsin the area. Bancroftfound a nestwith three eggson IslaHuivulai on 11 June 1930 (depositedat the WesternFoundation of VertebrateZoology [WFVZ]), and van Rossem(1945) reported it as a residenton "suitable. localities" throughoutthe state. Yellow-crownedNight-Heron (Blycti½orax violaceus). We found 20 pairs with nestsand one immaturein the SE heronryand 20 pairswith nestsin the NE heronry on IslaHuivulai. One hundredthrity individuals (including 2 immatures)were foraging throughoutthe bay and in nearbydrains. Bancroft collected nests from apparently foursites on lslaT6bari [--Huivulai] in EsteroT6bari on 27 April 1930 (6 setsof eggs depositedat WFVZ). Van Rossem(1945) reportedthis speciesas a localresident on coastallagoons. White Ibis (Euclocimusalbus). The SE heronryof Isla Huivulaihad 100 adults, including37 nestingpairs. The NE heronryhad aboutthe samenumber. We found 20 adultsand three immaturesat Pared6n Colorado, in the central part of Estero T6bari. The speciesoccurs from Guaymassouth to the lstmo de Tehuantepec (Knoderet al. 1980) andhas been reported in springand summerfrom EsteroT6bari (van Rossem1945). In May 1930 Bancrofftook eggsfrom two nearby locations, LagunaGu/•simas and IslaLobos (deposited at WFVZ). RoseateSpoonbill (Ajaia ajaja).We found15 pairswith nestsin the SE heronry. Therewere none in the NE heronry.Knoder et al. (1980) foundthis species from Los Mochis southto the lstmo de Tehuantepec,and the AOU (1983) consideredit a residentonly from northern Sinaloa south. This is the first breedingrecord for Sonora. CommonMoorhen (Gallinula chloropus). We sawthree broods(2 or 3 chicksper broodfor 8 chicks;4 adults)in variousagricultural drains near EsteroT6bari. SnowyPlover (Characlrius alexanclrinus). On the San Jos• saltfiatthere was one pair callingand performinga distractiondisplay, and one empty shell-linednest. There was one adult at Pared6n Colorado and one adult on the islets at the northern mouthof EsteroT6bari. No previousnesting records of this speciesin Sonorahave 'been published,and the AOU (1983) did not includeSonora within the breeding rangeof this species. Wilson'sPlover (Characlrius wilsonia). We saw20 pairsin Esterode San Jos&;all birdswere callingand performingdistraction displays, including broken-wing behav- ior; one adulthad a chickless than a weekold. Fivepairs were on the saltfiatnear San Jos•. One adultperformed distraction behavior at the abandonedshrimp farm north of EsteroT6bari. An eggshellfound near this siteby M. Tordecillas(pers. comm.), 5 May 1994, probablywas from this species. lOO NOTES ß ß ., , ,. - Ili{i Ii I illiraqi iiI r r,i I li•'l ,irlll• ,lllll III rl i L i "111•lrl•lll• •1 l, I %- LJl lol NOTES AmericanOystercatcher (Haematopus palliatus). There were sixpairs nesting on the shelldump southof El Paredoncito(also named El T6bati), at the southside of EsteroT6bati; one of the birdsperformed attraction display. There was one pair on a tiny isletin front of El Paredoncito,six pairs, one with three eggs,on the islets outsidethe north mouth of the bay, and two pairson the north end of Isla Huivulai. At the Esterode San Jos• there were three pairs, one with three chicks,and at the San Jos• saltfiat,two pairs,of whichone individualperformed pseudo-incubation. LeastTern (Sternaantillarum). We foundfive aggregationsof this species:south sideof the southmouth of the bay (82 adults),north sideof the north mouthof the bay (34 adults),islet outsidethe north mouth of the bay (28 adults),Estero de San Jos• (15 pairsnesting; 4 nestshad 2 eggseach and 1 nest, 1), and San Jos• saltfiat (15 pairsnesting; 3 nestshad 2 eggseach). Although, we confirmednesting only at SanJos•, the birdslooked like they were nesting on the isletoutside the northmouth. There is a chancethat thiscolony was wiped out by the high tidespreceding our visit. Conservationof thesecolonies of LeastTerns is importantbecause, being at the type localityof S. a. mexicana,they are relevantto the taxonomicstatus of LeastTerns in northwestern Mexico. BlackSkimmers (Rynchops niger) We found50 adultstogether with BlackTerns (Chlidoniasniger) on the isletof the north mouth.There were nest-likedepressions in the sand,but no definiteevidence of nesting.Van Rossemand Hachisuka(1937) indicatedthat "it was perfectly evident that the breedingseason was at hand," althoughthey too failedat findingnests. White-wingedDove (Zer•aidaasiatica). We heardseveral singing in bothheronties but did not searchfor evidenceof nesting. Other residentspecies that we observedand that probablynest in the area, but for whichwe foundno evidence,include five pairsof ducksresembling Mexican Ducks (Anasdiazi) in nearbydrains (it is likelythat they are feral domesticducks), Clapper Rail (Railus Iongirostris; 1 in the NE heronry), Black-neckedStilt (Himantopus mexicanus;7 adultson one of the isletsoutside the northernmouth of the bay; 5 elsewherein the bay), Killdeer(Charadrius vociferus; 5 adultsthroughout the bay), SavannahSparrow (Passerculussandwichensis; several near [] Paredoncito).On the other hand, it was somehowsurprising not findingany Wood Storks(Mycteria americana),which were reported