Mta ~i, 4~ tRY "'"V .'- IL Evaluating Mourning Dove Crop Gland Activity Associated with Crop Milk. Production BULLETIN 545 DECEMBER I') ~ i i-I 1 ALABAMA AGRICULTURAL EXPE ERIMENI STATION AUBURN UNIVERSITY GALE A. BUCHANAN, DIRECTO AUBURN UNIVERSITY, ALABAMA CONTENTS Page INTRODUCTION ........ .................... ........... ........... 3 MATERIALS AND METHODS....................... GENERAL PATTERN OF CROP GLAND DEVELOPMENT AND REGRESSION .............. ........... 4 5 ........... ILLUSTRATIONS ............................... ....................... .......... ............ 6 11 LITERATURE CITED The research on which this report is based was sponsored in part by each of the following: Accelerated Research Program for Webless Migratory Shore and Upland Game Birds, U. S. Fish and Wildlife Service Alabama Agricultural Experiment Station, Auburn University Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University Virginia Commission of Game and Inland Fisheries PHOTO CREDITS: Cover picture of parent feeding fledglings, R. R. Hitchcock; all others, R. E. Mirarchi. FIRST PRINTING 3M, DECEMBER 1982 Information contained herein is available to all persons regardless of race, color, sex, or national origin. Evaluating Mourning Dove Crop Gland Activity Associated with Crop Milk Production RALPH E. MIRARCHI AND PATRICK F. SCANLON 1,2 M OURNING DOVES (Zenaidamacroura) are America's most abundant game birds. With their swift and erratic flight, they provide hunters with many hours of outdoor recreation. Their popularity as game birds causes millions of dollars of Pittman-Robertson (Federal Aid in Wildlife Restoration) tax revenues to be generated. These funds can be used for management of doves and other wildlife species. Mourning doves are popular with nonhunters as well, because of their attractive appearance and plaintive vocalizations, and because they frequently nest in suburban and urban areas. Mourning doves lay two eggs per nesting attempt, incubate the eggs for 14 days, brood the young for approximately 15 days, and feed the fledglings 10-12 days after they leave the nest (1). Mourning doves nourish their young with a curdlike substance regurgitated from the crop. This crop "milk" is formed by desquamation of the proliferating epithelium of the crop wall (2). Formation of crop milk is confined to the two lateral lobes in the crop of both parents and is accompanied by changes in the crop wall that are readily observable in dissected specimens. Nestlings are fed crop milk almost entirely for 5-6 days posthatching(3). Seeds become more prevalent in the 'Assistant Professor, Department of Zoology-Entomology, and Professor, Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University. 2Gratitude is extended J. T. Jones and C. F. Mirarchi for help in caring for the captive dove colony. W. Morehead aided in collecting samples. lvi INTRODUCTION ALABAMA AGRICULTURAL EXPERIMENT STATION diet up until the time of fledging, when there is little difference between the diets of fledglings and adult doves (4). Although crop milk production decreases greatly during the early stages of brooding, crop gland activity persists to some degree for longer periods. This activity persists longer in males than in females (5) during a "typical" nesting cycle (i.e. one followed by a renesting attempt) because males have greater feeding responsibilities after the young doves fledge (1). A variable percentage of hunter-harvested mourning doves in the United States each year shows indications of crop gland activity (6). The controversy between humane organizations and governmental agencies surrounding crop gland activity of mourning doves harvested early in the hunting season has continued for more than 30 years. Recent research funded by state and federal agencies has concentrated on resolving these conflicts. Development of techniques useful for detection and evaluation of crop gland activity has become necessary, and new field (7,8) and statistical (9) techniques already have been developed. However, personnel who have had little experience with crop gland activity have difficulty accurately classifying the various phases by gross morphological traits. This bulletin was developed to serve as a guide for such personnel. MATERIALS AND METHODS Paired mourning doves of a captive breeding colony were allowed to court, mate, and nest. Paired birds were selected and sacrificed simultaneously at 9:00 a.m. e.d.t. on specific day intervals postlaying and posthatching. Postlaying and posthatching day intervals were determined using the first egg laid and the first egg hatched, respectively, as the first day of the interval. Crop development was classified as active, developing, regressing, or inactive based on criteria outlined previously for other columbids (10,11). Crops were weighed after removal of contents and extraneous materials. To ensure representation of normal color patterns, crop glands were photographed immediately after dissection. Photographs included full frontal views of the entire crop with one lobe exposed and a close-up of the exposed crop lobe. Descriptions of each important stage of crop gland development and regression were made and crop gland weights were recorded. EVALUATING MOURNING DOVE CROP GLAND ACTIVITY GENERAL PATTERN OF CROP GLAND DEVELOPMENT AND REGRESSION The duration and characteristics of mourning dove crop gland activity during the nesting cycle have been described in detail (5). Crop gland activity is absent in nonbreeding adults and during the first 9 days postlaying. Crop glands develop rapidly in both sexes from the 10th to the 14th day of incubation. Both parents have active crop glands during the first 5 days posthatching. Crop glands of adult males and females begin to regress at different rates at 9 days posthatching and some females already have inactive crop glands by that time. Crop glands of males regress slower than those of females and may lag behind by approximately 4-6 days. The majority of both sexes have inactive crop glands by 18-20 days posthatching. Note: The gross morphology of developing and regressing crop glands differs little, and the two cannot be separated accurately by gross visual examination. These crop glands would have to be classified using histological examination if the stage of incubation or brooding is unknown. External (top): Lobes are translucent with no thickening or hyperemia. No heavy pigmentation, other than a light cream cast. Internal (bottom): Lobes may or may not have slight stippling (folds). Folds have minimal height and width when present. No fusion of folds or crop milk present. Weight range (fresh)-male, 0.9-2.2 grams; female, 0.7-2.0 grams. SI11n-c2 Uf of sling, cyclc(cluisl S)ulntrc ii cl cdin,, Ii n.( tik e External (top): Lobes opaque, slightly thickened. Blood vessels begin to become prominent. Crop may attain yellow-rose hue. Internal (bottom): Lobes have folds of medium height and width. Some fusion of folds and small amounts of crop milk may be present. Weight range (fresh)-male, 1.3-3.4 grams; female, 1.2-3.1 grams. St 'c c f ncc irnl- Sc Grohphas cI/(l( (cl(1,) I. Sex Cron u I i t~ t:7 S(ur'r u/ n Ohl, c'1/r1c dol/> / .4 i . F- , - 7 r External (top): Lobes are opaque and very thick with numerous blood vessels present. Crop has rose-red color cast. Internal (middle): Lobes have definite folds of great height and width. Folds may be fused and crop milk often present in copious quantities. All particles present are food items. Internal (bottom): Crop gland with both lobes exposed to show crop milk. Weight range (fresh)-male, 2.9-5.5 grams; female, 3.5-6.7 grams. female, 3.5-6.7 range (fresh)-male, 2.9-5.5 - d 0 -. 0 V. N N( r N C; °_: (U)NOC DCOV DC - 5' CD01'O O 0 Cfl 0 o -4 PQ cn 'C4, & 0fl O w C Cak 0 SG + an n C 2 ^ N CaM - C CD D -v C n =m a? CD < (D -oa -. - .7.Na) _O a O 0 nr S00 at r CD S D) -. N 00 (SD 0C= = S CD 0 gy{; D NO W6 o C 3D 3 (D DC a (D Q OC a) 5i)-2 °O. 04 iif IwOiu_- rte( /r d0f/ ( t',t jdl/Hi I5-?5 pO thttcltiw-, Iinnistti -- " 'f~ 2 External (top): Same basic description as crop glands of nonbreeding doves and crop glands 1-9 postlaying. Some characteristics (amount of opacity, folds or stippling, thickness) may be slightly more exaggerated. Internal (bottom): Same comments as external. Weight range (fresh)-.7-1.7 grams. EVALUATING MOURNING DOVE CROP GLAND ACTIVITY 11 (1) (2) (3) LITERATURE CITED R. R. 1982. Duration of Dependence of Wild Fledgling Mourning Doves upon Parental Care. M.S. Thesis. Auburn Univ., Auburn University, Ala. 63 pp. HITCHCOCK, (4) LEVI, W. M. 1957. The Pigeon. Third ed. Levi Publ. Co. Inc. Sumter, S.C. 667 pp. LAUB, K. W. 1956. The Relation of Parental Care and the Condition of the Glandular Crop to the Successful Rearing of Young Mourning Doves, Zenaiduramacroura (L). M.S. Thesis. Ohio State Univ. Columbus, Ohio. 68 pp. MOORE, G. C. 1940. The Nesting Habits and Juvenile Development of the Mourning Dove in Alabama. M.S. Thesis. Ala. Poly Inst., Auburn, Ala. 65 pp. MIRARCHI, R. E. AND P. F. SCANLON. 1980. Duration of Mourning Dove (5) (6) (7) (8) Crop Gland Activity During the Nesting Cycle. J. Wildl. Manag. 44:209-213. . 1978. Crop Gland Persistence, Parental Care, and Reproductive Physiology of the Mourning Dove in Virginia. Ph.D. Dissertation. Virginia Poly. Inst. and State Univ. Blacksburg, Va. 249 pp. ZIEGLER, D. L. 1971. Crop Milk Cycles in Band-tailed Pigeons and Losses of Squabs Due to Hunting Pigeons in September. M.S. Thesis. Oregon State Univ. Corvallis, Oreg. 48 pp. MIRARCHI, R. E., P. F. SCANLON, AND N. L. SCHAUER. 1978. Field Tech- niques for Detection and Evaluation of Crop Gland Activity in Mourning Doves. Proc. Ann. Conf. S.E. Assoc. Fish and Wildl. Agencies. 32: 75-81. (9) , D. R. JENSEN, AND P. F. SCANLON. 1982. Classification of Mourning Dove Crop Gland Activity Phases by Discriminant Function Analysis. Wildl. Soc. Bull. (In review.) 10) BEAMS, H. W. AND R. K. MEYER. 1931. The Formation of Pigeon "Milk". Physiol. Zool. 43:486-500. 11) MARCH, G. L. AND R. M. F. S. SADLEIR. 1970. Studies of the Band-tailed Pigeon (Columbafasciata) in British Columbia. I. Seasonal Changes in Gonadal Development and Crop Gland Activity. Can. J. Zool. 48:1353-1357. ,AL)HLk{N tllHRN 11X WXit h an ag~ric uleve(ry miaJo r soi)l area., AuL urn (Tli \ersit \ serves tlhe needs oif field c r( p, livcst( tek, fo rest ry, and hotticUaIt>u al produce rs in each region in Alahanla. Every citi/cen of)the State has a stake in this reseatrc h programll, since all adlvatage from11 ne\\ andc tmo re eco nt tmical WIVS of tproducing and handling farm Il t)clouct clirect ly henetits thle contsumting cIuhlic. o ® Main Agricultural Experiment Station, Auburn. E. V. Smith Research Center, Shorter. Tennessee Valley Substation, Belle Mina. Sand Mountain Substation, Crossville. North Alabama Horticulture Substation, Cullman. Upper Coastal Plain Subs':ition, Winfield. Forestry Unit, Fayette Co !nty. Chilton Area Horticulture Substation, Clanton. Forestry Unit, Coosa County. Piedmont Substation, Camp Hill. Plant Breeding Unit, Tallassee. Forestry Unit, Autauga, Counrty. Prattville Experiment Field, Prattville. Black Belt Substation, Marion Junction. The Turnipseed-tkenberry Place, Union Springs. Lower Coastal Plain Substation, Camden. Forestry Unit, Barbour County. Monroeville Experiment Field, Monroeville. Wiregrass Substation, Headland. Brewton Experiment Field, Brewton. Solon Dixon Forestry Education Center, Covington and Escambia counties. 20. Ornamental Horticulture Field Station, Spring Hill. 21. Gulf Coast Substation, Fairhope. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19.