Measured values for Bulwer's Petrel eggs and eggshells from
Laysan Island, Northwestern Hawaiian Islands, were within 10% of predicted
values available in the literature. In the absence of published predictive equations
for egg volume, fresh-egg contents, and total functional pore area of the
shell, in Procellariiformes, new logarithmic relationships were developed for
tropical Procellariiformes. Data are now needed for species breeding at higher
latitudes to determine if these relationships are representative of all Procellariiformes

Pettit, T.N.

Whittow, G.C.

Pacific Science

ScholarSpace at University of Hawai'i at Manoa

Pacific Science, vol. 54, no. 2: 183-188© 2000 by University of Hawai'i Press. All rights reservedEgg Dimensions and Shell Characteristics of Bulwer's Petrels, Bulweriabulwerii, on Laysan Island, Northwestern Hawaiian Islands!G. C. WmTTow2 •3 AND T. N. PETrn2ABSTRACT: Measured values for Bulwer's Petrel eggs and eggshells fromLaysan Island, Northwestern Hawaiian Islands, were within 10% of predictedvalues available in the literature. In the absence of published predictive equa-tions for egg volume, fresh-egg contents, and total functional pore area of theshell, in Procellariiformes, new logarithmic relationships were developed fortropical Procellariiformes. Data are now needed for species breeding at higherlatitudes to determine if these relationships are representative of all Procellarii-formes.BULWER'S PETREL IS a small, procellariiformseabird of the tropical Atlantic, Pacific, andIndian Oceans (Warham 1990, Megyesi andO'Daniel 1997). In the Hawaiian Archipel-ago, it breeds on islands from Pearl andHermes Reef in the Northwestern HawaiianIslands, to offshore islands of Hawai'i in themain Hawaiian Islands (Harrison 1990).Previously, data were presented for, interalia, the incubation period and the incuba-tion weight loss of eggs on Manana, a smalloffshore island of O'ahu, in the main Hawai-ian Islands (Whittow 1994). The purpose ofthis report is to provide information on thedimensions of Bulwer's Petrel eggs and onsome of the characteristics of the eggshells,collected on Laysan Island (25° 46' N,171 ° 44' W) in the Northwestern HawaiianIslands, and to compare the measured datawith predicted values for Procellariiformescompiled by Rahn and Whittow (1988).MATERIALS AND METHODSEgg dimensions were measured with dialcalipers, and the weight of the freshly laid eggwas determined by weighing the egg after re-1 Manuscript accepted 12 August 1999.2 Department of Physiology, John A. Burns School ofMedicine, University of Hawai'i, Honolulu, Hawai'i96822.3 Author for correspondence.placing the air ill the aircell with distilledwater (Grant et al. 1982a). Egg volumes weremeasured by weighing the eggs in air and inwater (Rahn et al. 1976). Shell weight andshell thickness were determined on shells thathad been dried in a desiccator for at least 3days. Shell weight was measured by weighingthe dried shells on a Mettler balance (ModelH6) to the nearest 0.1 mg. Shell thickness wasdetermined with micrometer calipers (StarrettNo. 230) fitted with a ball attachment on thespindle to accommodate the curvature of theeggshell. The water-vapor conductance of theshell and shell membranes was measured byweighing the eggs daily, for 5 days; the eggswere kept in a desiccator at a constant tem-perature of 25°C. Under these conditions, thewater-vapor conductance can be calculatedfrom the weight loss and the known water-vapor pressure difference between the con-tents of the eggs and the air in the desiccator.The water-vapor pressure of the egg contentsis equal to the vapor pressure of water at25°C, and that of the air in the desiccatoris zero (Ar et al. 1974). The measure of vari-ation used in this report is the standard devi-ation" (SD); .n = number of observations;r = correlation coefficient.RESULTS AND DISCUSSIONThe dimensions of the eggs and the char-acteristics of the eggshells of the Bulwer's183184 PACIFIC SCIENCE, Volume 54, April 2000TABLE IMEASURED AND PREDICTED VALUES FOR EGGS AND EGGSHELLS OF BULWER'S PETRELSPARAMETER MEASURED PREDICTEDEggLength (cm) 4.22 ± 0.18 (29) 4.22Width (cm) 3.04 ± 0.08 (29) 3.12Volmne (cm3) 19.89 ± 1.57 (29)Fresh-egg weight (g) 21.077 ± 1.782 (19) 19.145EggshellWeight (g) 1.2476 ± 0.1948 (20) 1.3366Thickness (rom)Shell 0.138 ± 0.011 (8)·Shell +membranes 0.187 ± 0.013 (l V 0.186Inner shell membrane 0.008 ± 0.004 (3)'Water-vapor conductance 2.53 ± 0.36 (II) 2.79(mg day-I tore l ) 2.56NOTE: Mean measured values (± I SD) are shown; numbers of eggs are in parentheses. Predicted values are from Rahn and Whit-tow (1988).•25 measurements on 8 eggs.b 49 measurements on 11 eggs.'6 measurements on 3 eggs.Petrel are given in Table 1, together with thepredicted values for a procellariiform eggwith the incubation period (45.2 days [Whit-tow 1994]) and fresh-egg weight (Table 1) ofa Bulwer's Petrel weighing 92.8 g (Whittow1994).Measured egg dimensions were eitheridentical to (egg length) or 97.4% of (eggwidth) the predicted value; measured fresh-egg weight was 10.1% higher than the valuepredicted for Procellariiformes (Table 1).Few direct measurements of egg volume havebeen made on procellariiform eggs (Warham1990), probably because it is not easy tomeasure accurately under field conditions.Consequently, there is no published, pre-dictive equation for the egg volumes of Pro-cellariiformes. This is unfortunate, becausethe egg volume provides more comprehensiveinformation about the size and dimensions of, an egg thaIldQ(:~_llQyotheK single measure-ment. This report provides data for- the'voi:ume of the eggs of the smallest tropical pro-cellariiform species on which information isavailable, the Bulwer's Petrel. Taken togetherwith previously published information ob-tained in this laboratory, on the largest trop-ical species (Black-footed Albatross, Phoe-bastria nigripes) and five other tropicalspecies, it is possible to investigate a rela-tionship between egg volume (Vegg) and theweight (Wegg) of the fresWy laid egg fortropical Procellariiformes (Figure 1). Thespecies included in Figure 1 range in eggweight from 21.1 g (Bulwer's Petrel) to304.9 g (Black-footed Albatross). The rela-tionship between egg weight and volume islinear on logarithmic coordinates.The mean shell weight (Table 1) was 6.7%lower than the value predicted by Rahn andWhittow's (1988) equation for Procellarii-formes. The mean shell (including the shellmembranes) thickness was almost identical tothe predicted value according to Rahn andWhittow's (1988) criteria (Table 1). Rahnand Whittow (1988) assembled two pre-dictive equations for the water-vapor con-ductance of the shells and shell membranesthat take into account both the fresh-eggweight and the incubation period. The mea-sured' value was either 9.3% 'or 1.2°1o'lowerthan the predicted value, depending uponwhich equation was used (Table 1). In sum-mary, the measured egg length, width, fresh-egg weight, shell thickness, and water-vaporconductance of the shell were within 10% ofpredicted values.The water-vapor conductance (GH20)-. ~ t ••• *. '" fOr ,., " , • •Egg Dimensions and Shell Characteristics of Bulweria bulwerii-WmTTOW AND PETTIT200100185P. nigripesP. immutabilisC")E(,)-O'lO'lQ)>50P. hypoleucaP. phaeopygia50 100 200 300Wegg (g)FIGURE I. Relationship between egg volume (Vegg) and fresh-egg weight (Wegg) in seven tropical Procel-lariiformes. The line represents the equation: Yegg = 0.939· WeggO.998 (r = 0.999). Data sources: Phoebastria nigripesand P. immutabilis (Grant et al. 1982b), Pterodroma phaeopygia (Whittow et al. 1984), Puffinus pacificus (Ackermanet al. 1980), P. nativitatis (Whittow and Naughton 1999), Pterodroma hypoleuca (Grant et al. 1982c), Bulweria bul-werii (this report).and shell (including membranes) thickness(L) data (Table 1) may be used tocalculate the total functional pore area (Ap)of the shell from Rahn et al.'s (1976) equa-tion: Ap (mm2) = 0.447 . GH20 (mg· 24 hel .toreI):L (mm),yielding a_ value of 0.2115mm2 • The total functional pore area providesan indication of the pore area involved indiffusion of oxygen into the egg and diffusionof water vapor and carbon dioxide out of theegg. It is, therefore, an important measure ofthe facility with which gas exchange can oc-cur between the egg and its environment. Therate of gas exchange, in tum, determines thegrowth and metabolic rates of the embryo(Whittow 1984). This report provides datafor the functional pore area of the eggs of thesmallest tropical procellariiform species onwhich information is available, the Bulwer'sPetrel. It is possible to investigate a relation-ship between functional pore area (Ap) andthe weight (Wegg) of the freshly laid egg forthe seven tropical Procellariiformes that pro-vided the data for Figure 1. It is clear (Figure2) that log Ap is linearly related to log Wegg .Subtraction of the shell weight from theweight of the freshly laid egg (Table 1) yieldsthe weight of the contents of the freshly laid186 PACIFIC SCIENCE, Volume 54, April 20005.0NEE 1.0-c.<t0.5• P, phaeopygiaP. pacificusP. nigripesP. immutabilis50 100Wegg (g)200 300FIGURE 2. Relationship between total functional pore area (Ap ) and fresh-egg weight (Wegg) in seven tropical Pro-cellariiforrnes. The line represents the equation: Ap = 3.15.10-3 . Wegg l.36 (r = 0.998). Data sources: Phoebastria nig-ripes and P. immutabilis (Grant et al. 1982b), Pterodroma phaeopygia (Whittow et al. 1984), Puffinus pacificus (Whit-tow et al. 1982), P. nativitatis (Whittow and Naughton 1999; G. S. Grant, T.N.P., and G.C.W., unpubl. data),Pterodroma hypoleuca (Grant et al. 1982c), Bulweria bulwerii (this report).egg. The fresh-egg contents represent thetotal amount of organic substrates, salts, andwater available for the embryo's growth,metabolism, and water balance (pettit et al.1984). Again, there are no predictive equa-tions for egg contents in the literature, and,again, it is possible to establish a relationshipbetween egg contents and egg weight in theseven tropical species (Figure 3).When sufficient data become available forProcellariiformes breeding outside the Trop-ics, it will be possible to determine if therelationships for tropical Procellariiformesshown in Figures 1-3 represent all Procel-"~., ......~ ,""". " , ......,,,, , .... ,.~ ,... "'"~''''' ....,." ... " .... ,,~ ... ,,' ,. T' • >,,,Egg Dimensions and Shell Characteristics of Bulweria bulwerii-WmTTOW AND PETTIT 187100200P. nigripesP. immutabilisP. phaeopygiaP. hypoleuca50(J)-C<1>-Co(.)3=-C)-50 100W egg (g)200 300FIGURE 3. Relationship between weight of the contents of the freshly laid egg (Wcontents) and the fresh-egg weight(Wegg) in seven tropical Procellariiformes. The line represents the equation: Wcontents = 0.964· WeggO.993 (r = 0.999).Data sources: Phoebastria nigripes and P. immutabilis (Grant et al. 1982b), Pterodroma phaeopygia (Whittow et al.1984), Puffinus pacificus (Ackerman et al. 1980, Whittow et al. 1982), P. nativitatis (Whittow and Naughton 1999),Pterodroma hypoleuca (Grant et al. 1982c), Bulweria bulwerii (this report).lariiformes. The expectation is that they willdo so, because latitudinal variations in theallometric relationships of eggs are rare inprocellariiform birds (Whittow and Naugh-ton 1999).ACKNOWLEDGMENTSThanks are given to the u.s. Fish andWildlife Service (USF&WS) for grantingpermission to collect eggs on Laysan Island,and to Maura Naughton of the USF&WS forcollecting them.LITERATURE CITEDACKERMAN, R. A., G. C. WHIITOW, C. V.PAGANELLI, and T. N. PETTIT. 1980. Oxy-gen consumption, gas exchange, andgrowth of embryonic Wedge-tailed Shear-waters (Puffinus pacificus chlor.orhynchus).Physio1. Zoo1. 53: 210-221.AR, A., C. V. PAGANELLI, R. B. REEVES,D. G. GREENE, and H. RAHN. 1974. Theavian egg: Water vapor conductance, shellthickness and functional pore area. Con-dor 76: 153-158.GRANT, G. S., C. V. PAGANELLI, T. N.188PETTIT, G. C. WHITTOW, and H. RAHN.1982a. Detennination of fresh egg massduring natural incubation. Condor 84:121-122.GRANT, G. S., T. N. PETTIT, H. RAHN, G. C.WHITTOW, and C. V. PAGANELLI. 1982b.Water loss from Laysan and Black-footedAlbatross eggs. Physiol. Zool. 55: 405-414.---. 1982c. Regulation of water loss fromBonin Petrel (Pterodroma hypoleuca) eggs.Auk 99: 236-242.HARRISON, C. S. 1990. Seabirds of Hawaii.Cornell University Press, Ithaca, NewYork.MEGYESI, J. L., and D. L. O'DANIEL. 1997.Bulwer's Petrel (Bulweria bulwerii). Pages1-24 in A. Poole and F. Gill, eds. Thebirds of North America, No. 281. TheAcademy of Natural Sciences, Philadel-phia, and The American Ornithologists'Union, Washington, D.C.PETTIT, T. N., G. C. WHITTOW, and G. S.GRANT. 1984. Caloric content and ener-getic budget of tropical seabird eggs.Pages 113-137 in G. C. Whittow and H.Rahn, eds. Seabird energetics. PlenumPress, New York.RAHN, H., and G. C. WHITTOW. 1988.Adaptations to a pelagic life: Eggs of thealbatross, shearwater and petrel. CompoBiochem. Physiol. A Compo Physiol.91: 415-423.PACIFIC SCIENCE, Volume 54, Apri12000RAHN, H., C. V. PAGANELLI, I. C. T. NISBET,and G. C. WHITTOW. 1976. Regulation ofincubation water loss in eggs of sevenspecies of terns. Physiol. Zool. 49: 245-259.WARHAM, J. 1990. The petrels. AcademicPress, London.WHITTOW, G. C. 1984. Physiological ecologyof incubation in tropical seabirds. Stud.Avian Biol. 8:47-72.---. 1994. Incubation biology and nest-ling growth of Bulwer's Petrels onManana Island, Oahu, Hawaii. Pac. Sci.48: 136-144.WHITTOW, G. C., and M. B. NAUGHTON.1999. Christmas shearwater egg dimen-sions and shell characteristics on LaysanIsland, Northwestern Hawaiian Islands.Wilson Bull. 111 :421-422.WHITTOW, G. C., R. A. ACKERMAN, C. V.PAGANELLI, and T. N. PETTIT. 1982. Pre-pipping water loss from the eggs of theWedge-tailed Shearwater. Compo Bio-chern. Physiol. A Compo Physiol. 72: 29-34.WHITTOW, G. C., T. R. SIMONS, and T. N.PETTIT. 1984. Water loss from the eggs ofa tropical seabird (Pterodroma phaeopy-gia) at high altitude. Compo Biochem.Physiol. A Compo Physiol. 78: 537-540.", .. " ....... ,.. , ,., • ~. - ... - ' ..... - ,., .. • CO'

Egg Dimensions and Shell Characteristics of Bulwer's Petrels, Bulweria bulwerii, on Laysan Island, Northwestern Hawaiian Islands

http://scholarspace.manoa.hawaii.edu/bitstream/10125/1613/1/v54n2-183-188.pdf

Egg Dimensions and Shell Characteristics of Bulwer's Petrels, Bulweria bulwerii, on Laysan Island, Northwestern Hawaiian Islands

Abstract

Similar works

Full text

Available Versions

ScholarSpace at University of Hawai'i at Manoa