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1 July 2005 History, Present Status, and Future Prospects of Avian Eggshell Collections in North America
Lloyd F. Kiff
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Bird egg collecting was formerly a popular pastime in North America, having originated as a cultural import from England during the great Victorian era of natural history. Although Audubon took a few eggs in the 1830s and 1840s, widespread hobbyist egg collecting did not really take hold in North America until the 1860s, following the issuance by Stephen Fullerton Baird, Secretary of the Smithsonian Institution, of a “call to arms” (Baird 1861). His circular listed numerous as-yet-undescribed eggs needed by the Smithsonian and detailed instructions on how to preserve them. The study of eggs, or “oology,” as its adherents termed it, was at its zenith on this continent from about 1885 through the 1920s. Owing to changes in social attitudes and regulation, hobbyist egg collecting had declined markedly by the start of World War II and had completely faded from the American scene by 1970. Thus, the “oological chapter” of North American natural history lasted about a century (Kiff 1989a).

The vast majority of collectors were adolescents who took only eggs of the common species in their neighborhoods, but I have compiled biographical data for 1,200 adult collectors (1,195 males; 5 females) active at some point during the period from 1850 to 1970. Egg collecting was justified on both scientific and recreational grounds (Grinnell 1906), and many of the great lights of American ornithology, including Elliott Coues, Robert Ridgway, and Grinnell himself, collected bird eggs in their early years. T. Gilbert Pearson, a co-founder of the National Audubon Society, Audubon biologist Alexander Sprunt, Jr., and even Guy Bradley, the Florida Audubon warden whose shooting death by an egret plumer in 1905 sparked the modern Audubon movement, were all egg collectors.

Serious oologists collected and stored eggs as entire clutches, or “sets,” beginning in about the 1870s. The contents were removed through a single blowhole in the middle latitudes of the eggs. Thus, a museum “egg specimen” consists only of an empty eggshell with its associated eggshell membranes. Each specimen was inscribed in permanent black ink with a collector-specific “set mark,” typically consisting of such essential information as species identity (indicated by AOU number), collecting year, and number of eggs in the set. Details on collecting locality, collecting date, location of the nest, and collector name were recorded on a “data slip,” a card that often contained the printed name and address of the collector. Oological preparation and curatorial techniques are discussed more fully in Kiff (1989b) and Limbert (2003).

The findings, mostly anecdotal and descriptive, of oological studies were published in an astonishing array of small journals, many short-lived (Underwood 1954). The best of this lot in the late 19th century was the Ornithologist and Oologist, and later important oological journals included The Warbler, The Nidiologist, The Osprey, and The Journal of the Museum of Comparative Oology, all of which contain solid descriptive information still useful to contemporary ornithologists. The Oologist was the longest-lived journal of the genre, though it was not the best. It was published monthly from 1884 to 1941 and was discontinued only when the hobby ran out of enough practitioners to keep it going. Other than amassing their collections, the most lasting contribution of the oologists was the A.C. Bent life histories series, which relied heavily on their field observations. Indeed, the egg measurements from the Bent volumes still survive largely intact (albeit rounded off to whole millimeters) in the modern egg field guides by Harrison (1978) and Baicich and Harrison (1997).

Present extent of North American egg collections.—

Unlike avian study skins, skeletons, and spirit specimens, egg collecting was always primarily an endeavor of amateurs, and even the largest institutional collections are amalgamations of multiple private collections. A process of consolidation of collections was begun in the late 19th century by several wealthy collectors, including John Lewis Childs (Floral Park, New York), J. Parker Norris, Sr. and Jr. (Philadelphia), and Edward Arnold (Battle Creek, Michigan), and was continued in the mid-20th century by Wilson Hanna (San Bernardino County Museum, California), Ed Harrison (founder of the Western Foundation of Vertebrate Zoology [WFVZ] in Los Angeles), and Nelson Hoy (Media, Pennsylvania). The WFVZ continued to focus on collections acquisition later than all other institutions; by 1994, its holdings included ≈180,000 egg sets, representing the combined assets of more than 300 separate collections (Kiff 2000).

Surveys of North American institutions and the few living oologists confirmed the existence of ≈463,000 specimens in 72 collections (Kiff 1979, Kiff and Hough 1985), by the early 1980s. In the intervening two decades, I have become aware of only a handful of additional collections, mostly of modest size. I estimate that there are presently around 80 egg collections of research importance in North America and that, in aggregate, they contain <500,000 egg sets. Judging from comparisons of collector field catalogues with existing collections, I have the impression that the majority of the scientifically useful egg specimens collected in North America survived the move from private closets to institutions.

Nearly all the largest egg collections in North America are located in the largest naturalhistory museums, as might be expected. By now, the trend toward consolidation of collections has slowed. The WFVZ has acquired a few minor collections in the past decade, as has the University of Kansas Museum of Natural History, but orphaned egg collections may now go unclaimed. A large, previously unreported collection was purportedly sold to a European collector by a private high school, to which it had been inappropriately donated, and it is probably now lost to the research community. Globally, there are probably no more than 300 major bird egg collections, including some in private obscurity, and they contain a disproportionate representation of taxa from western Europe, North America, southern Africa, and Australia.

Uses of collections.—

Although most “oologists” were amateurs, they generally recorded useful and reliable data with their sets. Egg specimens and their associated data have probably been used in a greater variety of biological studies than any other type of avian specimens. At the WFVZ alone, the egg collection was used in more than 4,000 research projects from 1956 to 1994 (Kiff 2000), and many egg specimen uses were discussed by Green and Scharlemann (2003) and Limbert (2003). Thus, it is all the more curious that there never seems to have been a time when egg collecting was primarily a scientifically oriented activity, despite the pretenses of its main practitioners.

The most traditional lines of specimen-based egg studies involve their external morphology, including mass, length and breadth, shell thickness and texture, color, and shape. These characters have significance in studies of taxonomy (Zelenitsky and Modesto 2003), ecology (Svensson 1978), evolution (Moksnes and Røskaft 1995), physiology (Rahn et al. 1985), and genetics (Tryjanowski et al. 2001). Almost every issue of the major ornithological journals now contains at least one paper on one of these egg collection-related topics.

Many contemporary lines of research involve the use of eggshell fragments, often in connection with conventional whole eggshell collections. The study of eggshell ultrastructure by scanning electron microscopic techniques is a field of interest not only to poultry scientists, but also to taxonomists (e.g. Mikhailov 1997). Bird egg collections are valuable reference tools for archaeologists (Sidell 1993) who search through Indian middens and Grand Canyon caves. Additional uses of eggshell fragments include studies of x-ray diffraction (Gould 1972), pigmentation studies (Kennedy and Vevers 1976), and isotopic analyses (Hobson 1995). Studies of the effects of environmental acidification on passerines, especially in Europe (e.g. Graveland 1998), rely heavily on baseline information provided by egg collections. Using museum collections, Green (1998) and Scharlemann (2003) documented declines in eggshell thickness among Turdus species that probably resulted from reduced calcium availability caused by environmental acidification.

Egg collections were critically valuable in documenting widespread eggshell thinning (Ratcliffe 1967, Hickey and Anderson 1968) caused by DDE, a breakdown metabolite of the pesticide DDT. By now, hundreds of eggshell-based studies of this contaminant have appeared in all major regions of the world, and the present ban on DDT use in all but a handful of countries is a direct result of this research. Specimen-based data documenting severe eggshell thinning among Brown Pelicans (Pelecanus occidentalis) and other seabird species and DDEcaused extirpations of Bald Eagles (Haliaeetus leucocephalus) and Peregrine Falcons (Falco peregrinus) on the California Channel Islands (Kiff 1980) provided critical evidence in the “Montrose Case,” a U.S. Department of Justice suit against the last U.S. manufacturer of DDT. The case lasted for a decade and culminated in a natural-resource damages award of $140.2 million in 2001. Historically, that episode probably represents the most important use, from an economic standpoint, of any avian specimen type. Studies of the effects and extent of other contaminants, particularly heavy metals (Grandjean 1976), have also involved the use of eggshells and museum egg specimens. Becker (2003) recently summarized the many advantages of bird eggs and other avian specimens as biomonitoring tools.

The data associated with eggshell collections are almost as valuable as the specimens themselves, and they may prove to be particularly valuable in climate change studies. For example, Crick and Sparks (1999) recently showed that passerines in the United Kingdom are initiating egg-laying earlier in the year, probably in response to global-warming trends, and egg collection data could be used to detect such a trend in North America. The classic study by Väisänen (1969) showed how egg collections can be used to document changes in the historical distribution of a species paralleling changes in climatic conditions. Studies of this type are hampered by myopic regulatory attitudes, particularly in the United Kingdom, that have led to the virtual cessation of scientifically based egg collecting in recent decades, so only a partial record of broad environmental changes can now be reconstructed from egg collections.

Egg collection data have often been used to document the historical distribution of bird species for conservation management and other purposes (Kiff 1989c, Houston 2002). However, reconstructing entire historical ranges of bird species from egg specimen data (or any kind of specimen data) often requires the same sorts of extrapolations that plague paleontologists, owing to the patchy distribution of collectors. In North America, egg collectors tended to be concentrated in the most populous states and provinces, and large portions of the continent are unrepresented in existing collections. Of the 1,200 egg collectors for whom I have at least some data, 146 lived in California, almost all of them south of the San Francisco Bay area, and only 3 lived in neighboring Nevada.

Indeed, egg collections rarely, if ever, provide random samples at any level, and certain information from them should be used with caution. From my personal acquaintance with about 30 now-deceased egg collectors, I have concluded that the most obvious collector biases involved egg size and color selection (the odd ones were more desirable and are thus overrepresented in collections), collecting date (the start of the breeding season is better represented than the end for common species), clutch size (larger clutches were considered more desirable), and parasitized clutches (some collectors thought that sets with cowbird eggs were “ruined” and did not collect them or simply threw out parasite eggs). In addition, many (perhaps 5%) of the specimens in North American collections are misidentified or represent deliberate frauds. Perhaps techniques will be devised in the future that will allow us to confirm the identity of questionable specimens, but it is unlikely that they will involve DNA, a substance that only poorly prepared eggs contain.

Future prospects and recommendations.—

Most of the following suggestions were discussed more fully in Kiff (1978) and are as relevant now as then:

(1) Preserve traditional oological knowledge. There has been almost a complete loss of oological expertise within the museum community, not only firsthand familiarity with proper preparation and curatorial techniques, but also a loss of knowledge about such factors as the reliability of individual collectors, collector biases, interpretation of set marks, and species whose eggs were often misidentified. Few contemporary collection managers know how to blow an egg properly, or even have the tools to do so. As a consequence, almost no egg specimens are being preserved, owing to the loss of knowledge of proper preparation techniques, lack of institutional support, regulatory restrictions, and unfavorable funding trends. To my knowledge, there are no “working oologists,” though the studies of many researchers involve egg- or nest-related questions. No North American egg collection is staffed by an individual with traditional oological interests or knowledge, and even the WFVZ collection, which contains nearly 40% of all egg specimens in North American institutions (Kiff and Hough 1985), has not had a trained biologist directly supervising it for the past decade. Thus, the body of traditional oological knowledge may vanish, except on the browned pages of extinct journals, and existing egg collections may gradually become objects of greater interest to historians than to biologists.

(2) Provide funding for egg collection conservation and growth. Funding prospects for the support of egg collections remain bleak. There are no longer “angels” from the private sector who will invest in egg collections, primarily because there are no longer any self-serving motives for doing so. Government agencies, particularly those at local and state levels, are financially stressed, and museums of all types have suffered as a consequence. Federal funding can be found for the computerization of egg specimen data, but not for their interpretation. With a few commendable exceptions, traditional university natural-history museums are also fading from the scene, and many of the collections now housed at the WFVZ were relinquished by institutions with an ever-waning interest in organismic biology.

(3) Consolidate egg collections. Fred Lohrer suggested to me that a Nature Conservancytype organization devoted specifically to saving and housing natural-history collections might be formed. This could promote the consolidation of collections, perhaps in regional centers, and leverage funding opportunities. I think it is a good idea in theory, especially in regard to consolidation of collections. Most substantive research on eggs and other avian specimen preparations relies heavily on large sample sizes. Therefore, the smaller the collection, the more limited the possibilities for research use. The two main challenges to such a concept are finding the requisite funds and persuading institutions to contribute their collections to the cause. Perhaps the most effective funding strategies will emphasize the many applications of egg collections for conservation and biomonitoring purposes.

(4) Collect eggs and eggshell fragments for environmental monitoring purposes. Without continued, well-planned preservation of egg specimens, many useful opportunities for documenting environmental changes will be squandered. As discussed above, several exciting lines of research rely on eggshell fragments, and they do not necessarily involve the use of conventional museum specimens. In the future, egg collecting and egg collections will likely take a different form, and the exquisite preparation techniques of the Victorian era may give way increasingly to eggshell fragments stored in vials.

(5) Compile a global database of basic data on egg size, color, shape, eggshell thickness, and similar parameters. The most important major reference source for egg measurement and color data for birds of the world remains the monumental “Handbuch der Oologie,” begun by Max Schönwetter and brought to fruition by Wilhelm Meise (Schönwetter 1960-1992). There is no equivalent work in the English language, and these types of data are widely dispersed in the literature and field notebooks. The creation of a comprehensive database of basic egg data would be a tremendous time-saver for researchers and, like all such compilations, be helpful in revealing the many gaps in our knowledge and in existing egg collections.

Literature Cited


P. J. Baicich and C. J O. Harrison . 1997. A Guide to the Nests, Eggs, and Nestlings of North American Birds, 2nd ed. Academic Press, San Diego, California.  Google Scholar


S. F. Baird 1861. Circular in reference to collecting nests and eggs of North American birds. Smithsonian Miscellaneous Collections.  Google Scholar


P. H. Becker 2003. Biomonitoring with birds. Pages 675–736 in Bioindicators and Biomonitors: Principles, Concepts and Applications (B. A. Markert, A. M. Breure, and H. G. Zechmeister, Eds.). Elsevier, Amsterdam.  Google Scholar


H. Q P. Crick and T. Sparks . 1999. Climate change related to egg-laying trends. Nature 399:423–424. Google Scholar


R. W. Gould 1972. Brown Pelican eggshells: X-ray diffraction studies. Bulletin of Environmental Contamination and Toxicology 8:84–88. Google Scholar


P. Grandjean 1976. Possible effect of lead on egg-shell thickness in kestrels 1874–1974. Bulletin of Environmental Contamination and Toxicology 16:101–106. Google Scholar


J. Graveland 1998. Effects of acid rain on bird populations. Environmental Reviews 6:41–54. Google Scholar


R. E. Green 1998. Long-term decline in the thickness of eggshells of thrushes, Turdus spp., in Britain. Proceedings of the Royal Society of London, Series B 265:679–684. Google Scholar


R. E. Green and J. P W. Scharlemann . 2003. Egg and skin collections as a resource for long-term ecological studies. Bulletin of the British Ornithologists' Club 123A:165–176. Google Scholar


J. Grinnell 1906. Is egg collecting justifiable? Condor 8:155–156. Google Scholar


C. J O. Harrison 1978. A Field Guide to the Nests, Eggs, and Nestlings of North American Birds. Collins, Cleveland, Ohio.  Google Scholar


J. J. Hickey and D. W. Anderson . 1968. Chlorinated hydrocarbons and eggshell changes in raptorial and fish-eating birds. Science 162:271–273. Google Scholar


K. A. Hobson 1995. Reconstructing avian diets using stable-carbon and nitrogen isotope analysis of egg components: Patterns of isotopic fractionation and turnover. Condor 97:752–762. Google Scholar


C. S. Houston 2002. Spread and disappearance of the Greater Prairie-Chicken, Tympanuchus cupido, on the Canadian prairies and adjacent areas. Canadian Field-Naturalist 116:1–21. Google Scholar


G. T. Kennedy and H. G. Vevers . 1976. A survey of avian eggshell pigments. Comparative Biochemistry and Physiology 44B:11–25. Google Scholar


L. F. Kiff 1978. Report on egg collections in North America. In Final Report of the Workshop on a National Plan for Ornithology (J. R. King and W. J. Bock, co-directors).  Google Scholar


L. F. Kiff 1979. Bird egg collections in North America. Auk 96:746–755. Google Scholar


L. F. Kiff 1980. Historical changes in resident populations of California Islands raptors. Pages 651–673 in The California Islands: Proceedings of a Multidisciplinary Symposium (D. M. Power, Ed.). Santa Barbara Museum of Natural History, Santa Barbara, California.  Google Scholar


L. F. Kiff 1989a. Oölogy: From hobby to science. Living Bird Quarterly 8:8–15. Google Scholar


L. F. Kiff 1989b. Techniques for preparing bird eggs and nests. Pages 111–117 in Notes from a Workshop on Bird Specimen Preparation (S. P. Rogers and D. S. Wood, Eds.). Carnegie Museum of Natural History, Pittsburgh, Pennsylvania.  Google Scholar


L. F. Kiff 1989c. Historical breeding records of the Common Merganser in southeastern United States. Wilson Bulletin 101:141–143. Google Scholar


L. F. Kiff 2000. A history of the Western Foundation of Vertebrate Zoology, 1956–1994. Pages 183–228 in Contributions to the History of North American Ornithology, vol. II (W. E. Davis, Jr., and J. A. Jackson, Eds.). Memoirs of the Nuttall Ornithological Club, no. 13.  Google Scholar


L. F. Kiff and D. J. Hough . 1985. Inventory of Bird Egg Collections of North America, 1985. American Ornithologists' Union and Oklahoma Biological Survey, Norman, Oklahoma.  Google Scholar


M. Limbert 2003. The Uses and Curation of Birds' Egg Collections: An Examination and Bibliography. Peregrine Books, West Yorkshire, United Kingdom.  Google Scholar


K. E. Mikhailov 1997. Avian eggshells: An atlas of scanning electron micrographs. British Ornithologists' Club Occasional Publications, no. 3.  Google Scholar


A. Moksnes and E. Røskaft . 1995. Egg-morphs and host preference in the Common Cuckoo (Cuculus canorus): An analysis of cuckoo and host eggs from European museum collections. Journal of Zoology (London) 236:625–648. Google Scholar


H. Rahn, P. R. Sotherland, and C. V. Paganelli . 1985. Interrelationships between egg mass and adult body mass and metabolism among passerine birds. Journal für Ornithologie 126:263–271. Google Scholar


D. A. Ratcliffe 1967. Decrease in eggshell weight in certain birds of prey. Nature 215:208–210. Google Scholar


J. P W. Scharlemann 2003. Long-term declines in eggshell thickness of Dutch thrushes, Turdus spp. Ardea 91:205–211. Google Scholar


M. Schönwetter 1960–1992. Handbuch der Oologie. Bands 1–4. Akademie-Verlag, Berlin.  Google Scholar


E. J. Sidell 1993. A Methodology for the Identification of Archaeological Eggshells. Museum Applied Science Center for Archaeology, University of Pennsylvania, Philadelphia.  Google Scholar


B. W. Svensson 1978. Clutch dimensions and aspects of the breeding strategy of the Chaffinch Fringilla coelebs in northern Europe: A study based on egg collections. Ornis Scandinavica 9:66–83. Google Scholar


Tryjanowski, P. L. Kuczyński, M. Antczak, M. Skoracki, and M. Hromada . 2001. Withinclutch repeatability of egg dimensions in the Jackdaw Corvus monedula: A study based on a museum collection. Biologia, Bratislava 56:211–215. Google Scholar


M. H. Underwood 1954. Bibliography of North American Minor Natural History Serials in the University of Michigan Libraries. University of Michigan Press, Ann Arbor.  Google Scholar


R. A. Väisänen 1969. Evolution of the Ringed Plover (Charadrius hiaticula L.) during the last hundred years in Europe. A new computer method based on egg dimensions. Annales Academia Scientifica Fennica, Series A IV Biologica, no. 149.  Google Scholar


D. K. Zelenitsky and S. P. Modesto . 2003. New information on the eggshell of ratites (Aves) and its phylogenetic implications. Canadian Journal of Zoology 81:962–970. Google Scholar


Lloyd F. Kiff "History, Present Status, and Future Prospects of Avian Eggshell Collections in North America," The Auk 122(3), 994-999, (1 July 2005).[0994:HPSAFP]2.0.CO;2
Received: 30 June 2004; Accepted: 28 April 2005; Published: 1 July 2005

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