Eastern Bluebirds Eject Brown-Headed Cowbird Eggs Brian D

Eastern Illinois University The Keep

Faculty Research & Creative Activity Biological Sciences

January 2006 Eastern Bluebirds Eject Brown-headed Cowbird Eggs Brian D. Peer Western Illinois University

Lyndon R. Hawkins

Edwin P. Steinke

Patricia Blair Bollinger Eastern Illinois University

Eric K. Bollinger Eastern Illinois University, [email protected]

Follow this and additional works at: http://thekeep.eiu.edu/bio_fac Part of the Biology Commons, and the Poultry or Avian Science Commons

Recommended Citation Peer, Brian D.; Hawkins, Lyndon R.; Steinke, Edwin P.; Bollinger, Patricia Blair; and Bollinger, Eric K., "Eastern Bluebirds Eject Brown-headed Cowbird Eggs" (2006). Faculty Research & Creative Activity. 20. http://thekeep.eiu.edu/bio_fac/20

This Article is brought to you for free and open access by the Biological Sciences at The Keep. It has been accepted for inclusion in Faculty Research & Creative Activity by an authorized administrator of The Keep. For more information, please contact [email protected].

Eastern Bluebirds Eject Brown-Headed Cowbird Eggs / Sialia sialis Rechaza los Huevos de Molothrus ater Author(s): Brian D. Peer, Lyndon R. Hawkins, Edwin P. Steinke, Patricia Blair Bollinger, Eric K. Bollinger Reviewed work(s): Source: The Condor, Vol. 108, No. 3 (Aug., 2006), pp. 741-745 Published by: University of California Press on behalf of the Cooper Ornithological Society Stable URL: http://www.jstor.org/stable/4151096 . Accessed: 10/02/2012 13:05

Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected].

University of California Press and Cooper Ornithological Society are collaborating with JSTOR to digitize, preserve and extend access to The Condor.

http://www.jstor.org SHORTCOMMUNICATIONS 741

We thank Kimball Garrett and the Los Angeles BURTT, E. H., JR. 1979. Tips on wings and other County Museum of Natural History for loaning us things, p. 75-110. In E. H. Burtt JR. [ED.], The the albino Great Frigatebird and a normal juvenile, behavioral significance of color. Garland STPM also collected on Christmas Island, and the Harvard Press, New York. Museum of Comparative Zoology where we mea- BURTT, E. H., JR. 1981. The adaptiveness of colors. sured additional, typically colored juvenile frigate- BioScience 31:723-729. birds. We are grateful to the Wilson Ornithological BURTT, E. H., JR. 1986. An analysis of physical, Society, which provided a travel grant to AMP that physiological, and optical aspects of avian enabled her to meet with EAS in Washington where coloration with emphasis on wood-warblers. they discussed the data and drafted the manuscript. Ornithological Monographs 38. Our thanks to Pam Y. Burtt for the digital BURTT, E. H., JR. AND J. M. ICHIDA. 1999. photographs of the albino frigatebird.We also thank Occurrence of feather-degrading bacilli in the Carla Dove and an anonymous refereefor comments plumage of birds. Auk 116:364-372. on an earlier draft of the manuscript. DUCE, R. A., C. K. UNNI, B. J. RAY, J. M. PROSPERO, AND J. T. MERRILL. 1980. Long- LITERATURE CITED range atmospheric transport of soil dust from - AVERILL, C. K. 1923. Black wing tips. Condor Asia to the tropical north Pacific temporal 25:57-59. variability. Science 209:1522-1524. BACHMAN,J. 1839. Observations on the changes of GOLDSTEIN, G., K. R. FLORY, B. A. BROWNE, S. colour in birds and quadrupeds.Transactions of MAJID, J. M. ICHIDA, AND E. H. BURTT JR. the American Philosophical Society (Philadel- 2004. Bacterial degradation of black and white phia), new series 6:197-239. feathers. Auk 121:656-659. BARROWCLOUGH,G. F., AND F. C. SIBLEY. 1980. SCHREIBER, E. A., AND R. W. SCHREIBER.1988. Feather pigmentation and abrasion: test of Great Frigatebird size dimorphism on two a hypothesis. Auk 97:881-883. central Pacific atolls. Condor 90:90-99. BERGMANN, G. 1982. Why are the wings of Larusf TEST,F. H. 1940. Effects of natural abrasion and fuscus so dark? Ornis Fennica 59:77-83. oxidation on the coloration of flickers. Condor BONSER, R. H. C. 1995. Melanin and the abra- 42:76-80. sion resistance of feathers. Condor 97:590- VOITKEVICH,A. A. 1966. The feathers and plumage 591. of birds. Sidgwick and Jackson, London.

The Condor 108:741-745 ? The Cooper Ornithological Society 2006

EASTERN BLUEBIRDS EJECT BROWN-HEADED COWBIRD EGGS

BRIAN D. PEER1'5,LYNDON R. HAWKINS2,EDWIN P. STEINKE3,PATRICIA BLAIR BOLLINGER', AND ERIC K. BOLLINGER4 'Department of Biological Sciences, Western Illinois University, Macomb, IL 61455 2 2645 210th St., Mount Ayr, IA 50854 '2015 W. Fulliam, Muscatine, IA 52761 4Department of Biological Sciences, Eastern Illinois University, Charleston, IL 61920

Abstract. The relationship between the Brown- cowbirds, for egg ejection behavior. Bluebirdsejected headed Cowbird (Molothrus ater) and its cavity- 65% of experimentallyadded cowbird eggs (n = 20), nesting hosts has received little attention because of but ejected no experimentallyadded conspecific eggs the assumption that cowbirds rarely parasitize these (n = 66). This suggests that cowbird parasitism, not hosts. We tested the Eastern Bluebird (Sialia sialis), conspecific brood parasitism,is the selective pressure a host that is sometimes heavily parasitized by responsible for egg ejection in this species. This level of rejection may be conservative because bluebirds nest in dark cavities, which may make cowbird eggs difficult to detect by bluebirds. Manuscript received 13 September2005; accepted Key words: brood parasitism, Brown-headed Cow- 26 April 2006. bird, Eastern Bluebird, egg rejection, Molothrus ater, 5 E-mail: [email protected] Sialia sialis. 742 SHORTCOMMUNICATIONS

Sialia sialis Rechaza los Huevos de in Eastern Bluebirds (Gowaty and Bridges 1991, Molothrus ater Meek et al. 1994), and conspecific brood parasitism may occasionally select for egg rejection in non- Resumen. La relaci6n entre Molothrus ater y sus passerine species (Sorenson 1995, Lyon 2003). hospederos que nidifican en cavidades ha recibido However, little compelling evidence exists that poca atenci6n como resultado de la suposici6n de que passerine species have evolved egg rejection in M. ater rara vez parasita a estos hospederos. En este response to conspecific brood parasitism (Jackson estudio probamos si Sialia sialis, un hospedero que 1998, but see Victoria 1972, Rothstein and Robinson algunas veces es parasitado intensamente por M. 1998, Lahti 2005). Recognition of conspecific eggs is ater, exhibe comportamiento de rechazo de huevos. extremely rare, perhaps because females of the same Los individuos rechazaron el 65% de los huevos de species typically lay eggs that closely resemble one M. ater puestos experimentalmenteen los nidos (n = another (Peer and Sealy 2000). This is especially 20), pero no rechazaron ninguno de los huevos likely in Eastern Bluebirds, which lay immaculate coespecificos afiadidos (n = 66). Esto sugiere que el blue eggs. parasitismo por parte de M. ater es la presi6n We tested whether Eastern Bluebirdseject cowbird selectiva responsable por el rechazo de huevos en eggs and conspecific eggs by experimentallyparasit- esta especie, no el parasitismo intraespecifico. Este izing bluebird nests. We predicted that Eastern nivel de rechazo de huevos podria ser conservador, Bluebirds would eject cowbird eggs, but that they pues S. sialis anida en cavidades oscuras, lo que would accept conspecific eggs because of the lack of podria hacer que los huevos de M. ater sean dificiles interclutch variation in the appearance of bluebird de detectar. eggs.

METHODS Avian brood parasites such as the Brown-headed Cowbird (Molothrusater) must lay their eggs in the Cowbird egg experimentswere conducted in Warren nests of suitable hosts for their young to survive. and Dallas Counties, Iowa in May and June of 2005. Suitable hosts include those that have incubation Conspecific egg experimentswere conducted in Coles periods and nestling growth rates similar to or longer County, Illinois from 1993 to 2005. While it is than the cowbird, and those that feed their young an possible that these geographicallyseparated popula- appropriate diet. Species that nest in cavities are tions demonstrate variation in their response to usually considered inappropriate hosts, because the parasitism, there is little evidence of geographic parasites cannot fit into the cavities to lay, or they variation in egg rejection behavior in hosts that have simply avoid these nests for reasons that are unclear been tested (Rothstein 1975, Peer and Sealy 2004a, (Davies and Brooke 1998, Ortega 1998). There are but see Haas and Haas 1998). All nests were located exceptions, for example Prothonotary Warblers in nest boxes with varying designs. Some had (Protonotaria citrea) are frequently parasitized by standard,4 cm diameter,round entrances,and others Brown-headed Cowbirds (Petit 1991), House Wrens had elongated oval or rectangular entrances that (Troglodytes aedon) are parasitized by Shiny Cow- were >4 cm in diameter. Nests were experimentally birds (M. badius, Kattan 1998), and Redstarts parasitized with plaster eggs painted to simulate real (Phoenicurus phoenicurus) are parasitized by Com- cowbird eggs (Rothstein 1975). A sample of these mon Cuckoos (Cuculus canorus, Rutila et al. 2002). eggs measured(mean SE) 20.9 t 0.4 mm X 16.4 ? In addition, Honeyguides (Heteronettaspp.) special- 0.2 mm and weighed_ 3.6 ? 0.1 g (n = 9). Real ize on parasitizing hole-nesting species (Friedmann cowbird eggs measure 21.4 ? 0.2 mm X 16.1 + 1955). 0.2 mm (Peer and Sealy 2004b) and weigh 3.0 g Because of the assumption that cavity-nesters are (range: 2.6-3.4 g; Wetherbee and Wetherbee 1961). avoided by Brown-headed Cowbirds, little attention Nests were parasitized during the laying and in- has focused on antiparasite behaviors of such hosts. cubation stages of the nesting cycle. Nests were Peer and Sealy (2004a) reviewed the correlatesof egg checked for evidence of egg ejection every one to two rejection behavior in hosts of the Brown-headed days after parasitism.Eggs were considered ejected if Cowbird and reported that the only cavity-nesters they were missing from nests following parasitism. tested for rejection were the House Wren, Mountain Only a single egg was added to each nest and no host Bluebird (Sialia currucoides), and Prothonotary eggs were removed in conjunction with parasitism Warbler. Of these three species, only the Mountain because female Brown-headed Cowbirds do not Bluebird rejected cowbird eggs, albeit at a low always remove host eggs (Peer 2006). We parasitized frequency (20%;Hebert 1999). nests with cowbird eggs in relatively disparate areas Another cavity-nesting species in North America to avoid parasitizingthe same individuals more than that is parasitized and capable of raising cowbird once, and to our knowledge, only one pair was nestlings is the Eastern Bluebird (S. sialis, Woodward parasitized more than one time (see below). In- and Woodward 1979). Bluebirds possess several traits dividual nests were only tested once a year with that are correlated with egg rejection in cowbird hosts conspecific eggs and thus were not likely reparasi- (Peer and Sealy 2004a): they nest in open habitats, tized in a given year. It is possible that the same pairs they are relatively large hosts with correspondingly were parasitized in successive years, although, given large nests, and rejection also occurs in closely related the low annual survival of Eastern Bluebirds Mountain Bluebirds (H~bert 1999). Low levels of (Gowaty and Plissner 1998), the likelihood of conspecific brood parasitism have also been detected parasitizing the same individuals was likely minimal. SHORTCOMMUNICATIONS 743

Artificial bluebird eggs were used to test for Bluebirds accepted all conspecific eggs (n = 66), conspecific egg recognition. These eggs were made thus the rate of rejection of cowbird eggs was of wood and painted to mimic bluebird eggs. A significantly greater than that for conspecific eggs subset of the artificial eggs measured (mean t SE) (Fisher exact test, P < 0.001). There were unusual 21.9 0.1 mm X 16.1 + 0.1 mm and weighed 2.0 1 responses at two nests, but both were considered as 0.1 g _(n = 10). Real bluebird eggs measure (mean + acceptance. In one case, a nest box was deserted after SD) 20.9 t 0.9 mm X 16.4 ? 0.6 mm (Pinkowski one bluebird egg had been replaced with an artificial 1979) and weigh 3.1 + 0.3 g (range: 2.2-3.8 g; egg. Birds desert nests for a number of reasons Gowaty and Plissner 1998). Despite the differences (Rothstein 1975, Peer and Bollinger 1997), thus it is in weight, these eggs effectively simulate real eggs unclear whether this was a response to the parasitic (Peer and Bollinger 1997, 1998). A single bluebirdegg egg. At a second nest, a bluebird egg was removed was removed from each nest and replaced with an and replaced with an artificial egg, which was gone artificial bluebird egg. These experimentsdiffer from the following day. A second artificial egg was added the cowbird egg experimentsin which host eggs were and remained in the nest, but the nest was then not removed because the conspecific egg experiments deserted. It is unclear from this response what were also part of another study examining hatching occurred at this nest. Nests were never deserted after asynchrony in bluebirds. However, because egg cowbird eggs were ejected, which suggests that the removal does not appear to influence egg rejection first experimentallyadded egg may have been taken this should not have influenced our results (Peer by a predator rather than being ejected. No instances 2006). Nests were checked daily to determine host of natural conspecific brood parasitism were de- response, and this also allowed us to detect conspe- tected. Female bluebird bills measured 18.7 cific brood parasitism.Evidence of conspecific brood 0.1 mm (SE; n = 5). _ parasitismincluded the appearanceof more than one egg in a nest on a given day, because no birds are DISCUSSION known to more than a day, and the lay single egg per the we of after laying had stopped (Peer To our knowledge, egg ejection frequency appearance eggs in Eastern Bluebirdsis the of and Sealy 2000). documented highest any We also measured the of female bluebird cavity-nesting host. Mountain Bluebirdsejected 20% length nonmimetic and Redstarts bills, from the of the mandible to the of eggs (Hebert 1999), tip upper 44% of nonmimetic et al. commisure,to the nearest 0.1 mm, using dial calipers rejected eggs (Rutila 2002). Hebert that the (Peer and Sealy 2004a). This served as a comparison (1999) suggested egg rejection with other known to cowbird to frequency he recorded for Mountain Bluebirds may species reject eggs he added all after determine whether bluebird bills were large enough be conservative because eggs incubation had which make birds more for egg rejection (Peer and Sealy 2004a). started, may likely to accept parasitism (Rothstein 1976). We that the of observed RESULTS agree frequency egg rejection may be conservative for Mountain Bluebirds as well Bluebirds ejected 65% (13 of 20) of experimentally as Eastern Bluebirds.However, we do not believe this introduced artificial cowbird eggs. There was no is due to the timing of parasitism, because we found difference in response in relation to the timing of no relationship between the timing of parasitism and parasitism; 62% of eight eggs that were introduced rejection frequency, but rather due to the fact that during laying were ejected, and 67% of 12 eggs that these birds nest in dark cavities making it difficult to were introduced during incubation were ejected detect parasitic eggs. While we did not measure light (Fisher exact test, P = 1.0). Twelve of 13 ejections levels, we believe this to be the case for several occurred within 24 hr of parasitism; the other took reasons. First, bluebirds that nested in boxes with four days. No bluebirdeggs were missing or damaged larger entrances, which may have allowed more light following cowbird egg ejections. to penetrate, ejected eggs at a higher frequency. Cowbirdeggs wereejected from nine of 10 nests with Second, the pair that was parasitized twice accepted larger openings (i.e., >4 cm), whereasonly four of 10 the first cowbird egg in a nest with a standard eggs wereejected from nests with smalleropenings (i.e., entrance hole, but rejected the cowbird egg from 4 cm), with perhapsless light penetratingthem (Fisher a second box that had vent holes drilled into it to exact test, one-tailed,P = 0.03). One pair of bluebirds increase light penetration. It is possible that this pair was parasitized at two different nests on private was demonstrating phenotypic plasticity, but this is property.While we did not band the birds and cannot unlikely because rejectersof Brown-headedCowbird be certain it was the same pair, this pair successfully eggs always reject a second parasitism event after fledged one brood from a nest box we erected, rejecting the first (BDP and S. Rothstein, unpubl. maintainedtheir territory,and built a nest and reared data). Light penetration into nests has been demon- a second brood in a nest box we erected-4-5 m from strated to be a factor in egg rejection by Rufous the first box. This pair acceptedparasitism in the first Horneros (Furnariusrufus). These hosts apparently nest box with a small entrance hole. The second box cannot detect Shiny Cowbird eggs based on color in had the same-sized entrance, but we drilled vent holes their dark, domed nests, and instead reject cowbird on either side of it to increase the amount of light eggs based on differences in size (Mason and entering the box and the cowbird egg was ejected from Rothstein 1986). However, it is unlikely that blue- this nest. We observed no instances of natural cowbird birds distinguish cowbird eggs based on dimensions parasitism on bluebirds. because their eggs are essentially the same size, hence 744 SHORT COMMUNICATIONS

they must rely on vision. Further evidence that nests (Scott 1977). Given that rejectiontends to occur recognition was visual, rather than based on factors in members of the same taxonomic units (Peer and such as mass, is that none of the artificial bluebird Sealy 2004a), it would be worthwhile to test the eggs were rejected, despite the fact that they weighed Western Bluebird for egg ejection behavior. almost half that of real bluebird eggs (2.0 g vs. 3.6 g, respectively). Finally, all rejections occurred by egg We thank Rick Spellerberg and the other land- ejection rather than by desertion, and 12 of 13 owners who allowed us access to their properties. ejections occurred within 24 hr, which suggests that Anna, Kate, and Cam Peer assisted with the Eastern Bluebirds are very intolerant of parasitism experiments. Percy H6bert and Gustavo Kattan (Rothstein 1982, Peer and Sealy 2004b). provided helpful comments that improved the The size of nest box entrance holes may also play manuscript. a role in the ease of ejection. Female bluebird bills (18.7 mm) were slightly larger than the bills of the LITERATURE CITED smallest known rejecter species, the Warbling Vireo (Vireo gilvus), which has a mean bill length of DAVIES, N. B., AND M. DE L. BROOKE. 1998. 17.6 mm (Peer and Sealy 2004a). Thus, they should Cuckoos versus hosts: experimental evidence have no difficulty in grasping and ejecting eggs. for coevolution, p. 59-79. In S. I. Rothstein However, it is possible that female bluebirdscan eject and S. K. Robinson [EDS.],Parasitic birds and eggs more readily from nest boxes with larger their hosts: studies in coevolution. Oxford entrances. University Press, New York. As predicted, bluebirds accepted conspecific eggs. FRIEDMANN, H. 1955. The honey-guides. United This suggests that conspecific brood parasitismis not States National Museum Bulletin 208. a significant factor in the evolution of egg ejection in FRIEDMANN, H. 1963. Host relations of the parasitic bluebirds. Low levels of conspecific brood parasitism cowbirds. United States National Museum have been detected in Eastern Bluebirds(Gowaty and Bulletin 233. Bridges 1991, Meek et al. 1994), but the similarity GOWATY,P. A., AND W. C. BRIDGES.1991. Nestbox among the eggs of females makes recognition of availability affects extra-pair fertilizations and conspecific eggs difficult. Female bluebirds respond conspecific nest parasitism in Eastern Bluebirds, aggressively toward female bluebird models during Sialia sialis. Animal Behaviour 41:661-675. the early portions of the nesting cycle, which may be GOWATY,P. A., AND J. H. PLISSNER.1998. Eastern an alternativemeans of preventingconspecific brood Bluebird (Sialia sialis). In A. Poole and F. Gill parasitism (Gowaty and Wagner 1988). [EDS.],The birds of North America, No. 381. While bluebirds are one of the more common The Birds of North America, Inc., Philadelphia, cavity-nesting hosts of the Brown-headed Cowbird PA. (Friedmann 1963), parasitism frequencies are rela- GOWATY,P. A., AND S. J. WAGNER. 1988. Breeding tively low compared to other, open-cup nesting hosts season aggression of female and male Eastern (Ortega 1998). The typical entrance size of bluebird Bluebirds (Sialia sialis) to models of potential boxes is 4 cm and this may not be large enough to conspecific and interspecificegg dumpers.Ethol- allow female cowbirds to enter. Cowbirds have been ogy 78:238-250. known to parasitize the cavity-like nests of Verdins HAAS, C. A., AND K. H. HAAS. 1998. Brood (Auriparus flaviceps, Peer and Sealy 1999), which parasitism by Brown-headed Cowbirds on have openings of around 2.5 cm (Webster 1999). Brown Thrashers: frequency and rates of re- However, the entrance to a Verdin nest observed by jection. Condor 100:535-540. Peer and Sealy (1999) had been enlarged by the HtBERT, P. N. 1999. Evidence of egg ejection in female cowbird. Hoover (2003a) found that 50% of Mountain Bluebirds. Wilson Bulletin 111: 1979 artificial nests and 41% of 115 natural cavity 440-442. nests of ProthonotaryWarblers were parasitized.The HOOVER,J. P. 2003a. Multiple effects of brood openings of the artificial cavities ranged from 3.2 cm parasitism reduce the reproductive success of to 6.4 cm and the nests with larger entrances were Prothonotary Warblers, Protonotaria citrea. parasitized more often (Hoover 2003b). The highest Animal Behaviour 65:923-934. parasitismfrequency recordedfor bluebirdswas 16% HOOVER,J. P. 2003b. Experimentsand observations of 27 nests; in this study, bluebird houses were made of Prothonotary Warblers indicate a lack of of milk cartons with large openings (5.4 cm; Wood- adaptive responses to brood parasitism. Animal ward and Woodward 1979). Musselman (1946) found Behaviour 65:935-944. that 2.6% of 268 nests were parasitized and many of JACKSON,W. M. 1998. Egg discriminationand egg- these had their lids removed, allowing cowbirds to color variabilityin the Northern Masked Weav- gain entry. In contrast, Ontario nest record cards er: the importance of conspecific versus inter- reveal a parasitism rate of 0.1% of 3167 Eastern specific parasitism,p. 407-416. In S. I. Rothstein Bluebird nests (Peck and James 1987). and S. K. Robinson [EDS.],Parasitic birds and Cowbird parasitism of bluebird nests may go their hosts: studies in coevolution. Oxford largely undetected because many researchers utilize University Press, New York. nest boxes and bluebirds that nest in natural cavities KATTAN, G. H. 1998. Impact of brood parasitism: with larger entrances may be parasitized more why do House Wrens accept Shiny Cowbird frequently. Moreover, cowbird eggs may be ejected eggs?, p. 212-220. In S. I. Rothstein and S. K. from natural cavities before researchers observe these Robinson [EDS.], Parasitic birds and their hosts: SHORTCOMMUNICATIONS 745

studies in coevolution. Oxford University Press, of brood parasitism:implications for long-term New York. parasite-host coevolution. Auk 121:1172-1186. LAHTI, D. C. 2005. Evolution of bird eggs in the PETIT, L. J. 1991. Adaptive tolerance of cowbird absence of cuckoo parasitism.Proceedings of the parasitism by Prothonotary Warblers: a conse- National Academy of Sciences USA 102: quence of nest-site limitation?Animal Behaviour 18057-18062. 41:425-432. LYON, B. E. 2003. Egg recognition and counting PINKOWSKI,B. C. 1979. Effects of nesting history on reduce costs of avian conspecific brood parasit- egg size in Eastern Bluebirds. Condor 81:210. ism. Nature 422:495-499. ROTHSTEIN, S. I. 1975. An experimental and MASON, P., AND S. I. ROTHSTEIN.1986. Coevolution teleonomic investigation of avian brood parasit- and avian brood parasitism:cowbird eggs show ism. Condor 77:250-271. evolutionary response to host discrimination. ROTHSTEIN, S. I. 1976. on defenses Evolution 40:1207-1214. Experiments Cedar Waxwings use against cowbird parasitism. MEEK, S. B., R. J. ROBERTSON,AND P. T. BOAG. Auk 93:675-691. 1994. and brood Extrapairpaternity intraspecific ROTHSTEIN,S. I. 1982. Mechanisms of avian egg parasitism in Eastern Bluebirds revealed by which elicit re- DNA Auk 111:739-744. recognition: egg parameters fingerprinting. sponses by rejecter species? Behavioral Ecology MUSSELMAN,T. E. 1946. Some interesting nest habits and 11:229-239. of the Eastern Bluebird sialis Bird- Sociobiology (Sialia sialis). ROTHSTEIN,S. I., AND S. K. ROBINSON. 1998. The Banding 17:60-63. evolution and of avian brood ORTEGA,C. P. 1998. Cowbirds and other brood ecology parasitism: an overview, p. 3-56. In S. Rothstein and S. K. parasites. University of Arizona Press, Tucson, I. AZ. Robinson [EDS.], Parasitic birds and their hosts: studies in coevolution. Oxford G. AND R. D. JAMES. 1987. birds University Press, PECK, K., Breeding York. of Ontario: and distribution. Vol. 2. New nidiology R. AND K. KOSELKA.2002. The Passerines. Royal Ontario Museum, Toronto, RUTILA, J., LATJA, Canada. Common Cuckoo Cuculus canorus and its cavity B. D. 2006. destruction and removal nesting host, the Redstart Phoenicurus phoeni- PEER, Egg egg curus: a cuckoo-host Journal of by avian brood parasites: adaptiveness and peculiar system? Auk 123:16-22. Avian Biology 33:414-419. consequences. D. M. 1977. Cowbird on the PEER, B. D., AND E. K. BOLLINGER.1997. Explana- SCOTT, parasitism Gray Catbird at Ontario. Auk 94:18-27. tions for the infrequent cowbird parasitism on London, Common Grackles. Condor 99:151-161. SORENSON,M. D. 1995. Evidence of conspecific nest and discrimination in the Sora. PEER, B. D., AND E. K. BOLLINGER.1998. Rejection parasitism egg of cowbird eggs by Mourning Doves: a manifes- Condor 97:819-821. tation of nest usurpation?Auk 115:1057-1062. VICTORIA,J. K. 1972. Clutch characteristics and egg PEER, B. D., AND S. G. SEALY. 1999. Parasitism and discriminative ability of the African Village egg puncture behavior by Bronzed and Brown- Weaverbird Ploceus cucullatus. Ibis 114:367-376. headed Cowbirds in sympatry. Studies in Avian WEBSTER,M. D. 1999. Verdin (Auriparus flaviceps). Biology 18:235-240. In A. Poole and F. Gill [EDS.],The birds of North PEER, B. D., AND S. G. SEALY. 2000. Conspecific America, No. 470. The Birds of North America, brood parasitism and egg rejection in Great- Inc., Philadelphia, PA. tailed Grackles. Journal of Avian Biology WETHERBEE,D. K., AND N. S. WETHERBEE.1961. 31:271-277. Artificial incubation of eggs of various bird PEER, B. D., AND S. G. SEALY. 2004a. Correlates of species and some attributes of neonates. Bird- egg rejection in hosts of the Brown-headed Banding 32:141-159. Cowbird. Condor 106:580-599. WOODWARD,P. W., AND J. C. WOODWARD.1979. PEER, B. D., AND S. G. SEALY. 2004b. Fate of Brown-headed Cowbird parasitism on Eastern grackle (Quiscalus spp.) defenses in the absence Bluebirds. Wilson Bulletin 91:321-322.