Wilson Bull., 11 l(4), 1999, pp. 478487

GROWTH PATTERNS OF HAWAIIAN CHICKS

J. MICHAEL REED,,2,8‘ ELIZABETH M. GRAY,334 DIANNE LEWIS3 LEWIS W. ORING,3 RICHARD COLEMAN,5 TIMOTHY BURR,6 AND PETER LUSCOMB7

ABSTRACT-We studied chick growth and plumage patterns in the endangered (Himantopus mexicanus knudseni). Body mass of captive chicks closely fit a Gompertz growth curve, revealing a growth coefficient (K) of 0.065 day- ’ and point of inflection (T) of 17 days. When chicks fledged about 28 days after hatching, they weighed only 60% of adult body mass; at 42 d, still were only 75% of adult mass; culmen, tarsus, and wing chord at fledging also were less than adult size. This trend of continued growth to adult size after fledging is typical for most shorebirds. After hatching, captive chicks grew more rapidly than wild chicks, probably because of an unlimited food supply. We found no evidence for adverse effects of weather on the growth of wild chicks. As with other shorebirds, the tarsus started relatively long, with culmen and then wing chord growing more rapidly in later development. Tarsal and wing chord growth were sigmoidal, whereas culmen growth was linear. We describe plumage characteristics of weekly age classes of chicks to help researchers age birds in the wild. Received 28 Dec. 1998, accepted 20 April 1999.

Avian growth patterns have been studied (Himantopus mexicanus knudseni), a precocial primarily because of their relationships to the that is an endangered subspecies of the ecology and evolutionary history of different Black-necked Stilt. Like all shorebirds, species (Ricklefs 1968, 1973, 1983; OConnor’ are precocial and nidifugeous. Hawaiian Stilts 1984; Anthony et al. 1991), and to maximize are significantly larger than the nominate race food yields of domestic (e.g., An- (Coleman 1981) and differ somewhat in adult thony et al. 1991). Although there is selection plumage characteristics (Wilson and Evans for rapid independence of chicks, which 1893, Coleman 1981). Stilts are found on all should reduce variance in growth rates, intra- five major islands in , breed exclusive- specific growth patterns can be variable and ly in shallow, lowland wetlands (USFWS flexible because of environmental variability 1985), and statewide population counts indi- and competing selective pressures (Coach et cate a steady increase in population size (Reed al. 1991, Emlen et al. 1991). In studies of wild and Oring 1993). Our specific objectives were birds, altricial species have been studied more to (1) describe patterns of Hawaiian Stilt chick often than precocial species, at least in part growth from captive and wild birds and com- because the former remain in the nest from pare them to other shorebirds, and (2) provide hatching until fledging. a method for aging chicks in the field. The In this paper we present information on last objective was designed for studying pre- chick growth patterns of the Hawaiian Stilt adult mortality patterns by providing aging criteria that do not requiring capturing the bird. ’ ’ Biological Resources Research Center, Univ. of Nevada, Reno, NV 89557. METHODS *Current address: Dept. of Biology, Tufts Univ., Medford, MA 02155; E-mail: [email protected] Captive birds.-Growth data for captive birds came 3 Environmental and Resource Sciences/l86, 1000 from 15 individuals raised from eggs in 1980 in the Valley Rd., Univ. of Nevada, Reno, NV 89512-0013. Honolulu Zoo. Because chicks were kept in a common 4 Current address: USGS-BRDPIERC, PO. Box 44, enclosure, some competition for food might have oc- Hawaii National Park, HI 96718. curred, although food was provided ad libitum. Be- 5 U.S. Fish and Wildlife Service, 911 NE 1 lth Ave., cause all birds were subject to the same feeding and Eastside Federal Complex, Portland, OR 97232. environmental conditions, inter-individual variability 6 Southwest Division, Naval Facilities Engineering in growth should be minimized. All birds were Command, 1220 Pacific Hwy., San Diego, CA 92132- weighed daily for 42 days to the nearest 0.1 g. Ha- 5190. waiian Stilts fledge approximately 28 d after hatching ’ ’ 151 Kapahulu Ave., Honolulu Zoo, Honolulu, HI (Coleman 1981). 96815. One of the 15 birds was used only for the first 13 d BCorresponding author. because a bill deformity developed at this time, caus-

478 Reed et al. l HAWAIIAN STILT CHICK GROWTH 479 ing the individual to lose mass quickly. A sixteenth Plumage.-We considered only those plumage char bird was not included in the analysis because of ab- acteristics that were visible in the field: fuzzy appeat- errant fluctuations in growth. Its mass at hatch was ante associated with down, brown versus black cast, over 5 standard deviations above the mean, and it presence of an eye ring, etc. We used the above char- gained mass rapidly for 11 days. Between days 12-17, acteristics to describe plumage of weekly age classes. however, it lost 25% of its body mass, dropping well In several cases, plumage descriptions for weekly age below the mean (ca 2 standard deviations); on day 18 classes were incomplete (e.g., lacking description of it began to grow rapidly again, reaching mean mass wing coloration for week 3). Because plumage is es- for the group 24 d later. sentially the same for chicks of both Hawaiian and Other variables (culmen, tarsus, and wing chord) Black-necked stilts (Coleman 198 l), we supplemented were measured less regularly. Measurements were our descriptions of Hawaiian Stilts with plumage ob- made every 2-4 d after hatching and became less fre- servations of wild, known-aged Black-necked Stilt quent (every 4-10 d) after fledging. Some individuals chicks at Honey Lake, California in 1997. Plumage of were measured more often than others. Despite this adult Hawaiian Stilts is different from fledglings (Rob- variation, we were able to derive useful growth pat- inson et al., in press). terns for these body measurements. Mass was mea- Analyses.-Statistical analyses were conducted us- sured by one person and lengths by another. ing version 7.0 of SPSS (SPSS, Inc. 1995). One as- A growth curve for body mass was fit to a Gompertz sumption in comparing body measurements between equation (9 = 0.99; SPSS, Inc. 1995, NONLIN pro- captive and wild birds is that initial body sizes are cedure) because it is used most often for shorebirds equal. To test this, we used multiple analysis of vari- (e.g., Beintema and Visser 1989a) and we wanted to ance (MANOVA) to compare mass and culmen length, allow interspecific comparisons to be made (OConnor’ tarsus and wing chord measurements between known- 1984). The fit was made on average values for each aged captive and wild hatch day (day 0) birds. For ages day from 12-15 individuals. The Gompertz equation after day 0, we determined whether or not mean values has the form for wild birds fell within 95% confidence intervals for mean values of captive birds. All statistical tests were two-tailed. Values presented are means 2 SD. where W is body mass (g), A is asymptotic (adult) mass (g), K is the growth coefficient (day-),‘ t is age (d), RESULTS and e is the base for natural logarithms. Adult mass came from 43 adult males and 42 adult females (Cole- Growth in captivity-Growth parameters man 1981). Although adult females weigh slightly for the Gompertz equation indicated a growth more than males (mean difference = 7.0 g), the dif- coefficient (K) of 0.065 and time to inflection ference is a small percentage ((4%) of total body point (T) of 17 days. Although chick mass mass, consequently A was averaged across sexes varied little among the 11 individuals on day (202.5 g). of hatch (15.7 2 0.6 g), variability in mass Wild birds.-Wild chicks were captured by hand on the islands of , , and in 1978-1980 among individuals increased greatly over the and 1993. During 1978-1980, we captured chicks with first two weeks (60.4 ? 9.2 g), and remained known hatching dates 142 times. Because chicks from high up to fledging at day 28 (122.5 2 10.6 the same clutch were not considered to be independent, g). In general, differences among chick mass they were averaged within each clutch (maximum of at day 14 are consistent until fledging, indi- four chicks averaged per clutch). This resulted in 33 cating that chicks that gain relatively more measurements of chicks less than 24 h old (designated day 0; n = 64 chicks). Chicks were remeasured every mass in the first two weeks after hatching tend time they were encountered and captured. This resulted to fledge at a heavier mass than chicks that in 43 measurements of birds from 2-32 d old (n = 78 gain less mass their first two weeks. Captive chicks). We measured mass to the nearest 1.0 g, cul- individuals did not experience a significant men and tarsus lengths to the nearest 0.1 mm, and mass loss between day 0 (hatch day) and day wing chord to the nearest 1.0 mm. In 1993, we took 1 (paired t-test: t = -0.432, df = 10, P > measurements on 55 birds ranging in age from hatch- ing to fledging using the above methods. During 1993 0.05). we rarely knew the exact age of each chick, so these At fledging, chicks had not attained adult measurements were used only to determine the rela- body mass or body measurements. Mass at tionships among body measurements. Tarsus and wing fledging was 60% of adult mass, culmen chord measurements were made on the right side of length was 67% of adult length, tarsus length the chick and the same person made all measurements was at 66%, and wing chord length was at in 1993. We also noted the presence or absence of an egg tooth. Field measurements from 1978-1980 were 55% (adult measurements from Coleman made by one person, and in 1993 by another, so values 1981). were not compared. Growth in the wild.---There was no differ- 480 THE WILSON BULLETIN l Vol. II 1, No. 4, December 1999

60

50 loo- *la,* *Cl.

60- 40 q Captive 30 60- .El. A Wild rm* 20

10

0 10 20 30 40

me w

FIG. 1. Captive and wild Hawaiian Stilt chick mass and percentageof adult body mass (202.5 g) as a function of age. Values are means + SE. ence between mean mass of captive (2 = 15.7 Relative growth rates.-Relative growth 2 0.6 g) and wild (2 = 15.6 ? 1.1 g) chicks rates among different parts of the body can be at hatch (t = 0.551, df = 40, P > 0.05). The assessed without reference to age. We found apparent decrease in mass between day 0 tarsus length to be long in early development (hatch day) and day 1 for wild chicks was not relative to culmen and wing chord, and it con- significant (paired t-test: t = 0.585, df = 12, tinued to grow at a faster rate than the culmen P > 0.05). From days 1 to 17, masses of throughout development. Culmen and wing same-aged wild birds typically fell within the chord grew at approximately the same rate in 95% confidence interval of captive birds, early development until wing chord reached though below the mean. In three comparisons about 40 mm; as wing chord continued to (day 9, 14, 15), the mass of wild birds fell grow, culmen length growth rate slowed con- below the 95% confidence interval for captive siderably. Changes in wing chord and body mass. Mass gain with age generally followed mass were similar throughout the growth pe- a sigmoidal pattern, with individuals not riod observed (Fig. 3). Changes in tarsus reaching an asymptote until after 42 days of length and body mass also were similar until age (Fig. 1). Similarly, from days 1 to 17, individuals reached approximately 80 g, when mean wing chord of same-aged wild birds fell tarsus growth slowed. within the 95% confidence interval of captive Plumage.-Using field data from known- birds, with the exception of days 9, 14 and 15, aged chicks, we constructed a table of weekly when mean wing chord measurements for plumage characteristics for Hawaiian Stilt wild birds fell below the 95% confidence in- chicks (Table 1). The presence or loss of terval. Growth of the wing chord also fol- down, as well as overall body color, appear to lowed a sigmoidal pattern, although the slope be the two best indicators of chick age in the of the curve was less steep for wing chord wild for weeks l-3. Aging during this time is growth than it was for mass gain (Fig. 2). more precise if one can determine the pres- Mean culmen length and mean tarsus length ence and condition of primary sheaths; this did not differ between wild and captive birds cannot be done, however, without chicks in from days 1 to 17. Mean culmen growth for hand. Specifically, in week 1 chicks are en- both wild and captive chicks was relatively tirely covered with down, and primary sheaths linear with increasing age (Fig. 2). are absent. The dorsal surface of the body in- Reed et al. * HAWAIIAN STILT CHICK GROWTH 481

160 100 1 +z 1 5 80

o! I 8 1 ’ 0 40 60 120 160

60 160

50

40

30

20

in

0-l . I 8 1 1 0 40 60 120 160

z 210

5 180

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FIG. 2. Growth patterns for wing chord, culmen Ma66 (9) length, and tarsus length of captive and wild Hawaiian FIG. 3. Relative growth rates of three body mea- Stilt chicks. surements of wild Hawaiian Stilt chicks compared to body mass. eluding head, neck, back, and wing is mottled black, golden brown, and white; the ventral From 4-6 weeks, age classes can be differ- surface is creamy white. In week 2, the head entiated by the presence of tail feathers, the begins to turn brown and is distinctly lighter ability to fly, and the presence of an eye patch than the rest of the body. Mottling on the neck and eye ring. In week 4, tail feathers emerge changes to a more solid pattern of gray and and the eye patch and eye ring become visible. tan. Most importantly, primary sheaths During week 5, all down is lost, wing feathers emerge on day 12. During week 3, down be- are fully developed enabling short distance gins to disappear, giving chicks a sleeker ap- flight (up to 1.5 m), and the eye patch is dis- pearance. Overall body coloration changes tinct. Finally in week 6, chicks are capable of from mottled black, golden brown, and white prolonged flight. to plain gray and white, and primary sheaths As with other shorebirds (Clark 1961), the are broken about day 16. In all cases where egg tooth typically was lost after the first day we had information on both subspecies, plum- and always was gone after 48 h. age descriptions of known-aged Black-necked Stilt chicks matched exactly the plumage de- DISCUSSION scriptions of known-aged Hawaiian Stilt Because shorebird chicks feed themselves, chicks up to and including six weeks of age. they hatch with well developed legs and a

484 THE WILSON BULLETIN l Vol. 111, No. 4, December 1999 partly developed bill; wing development be- Reasons for variation in shorebird post-hatch- gins later and is rapid once started (Galbraith ing mass loss require further investigation. 1988, Thompson et al. 1990). Growth patterns Comparison of captive and wild chick are variable among species (Holland and Yal- growth.--Captive and wild chick masses did den 1991; Starck and Ricklefs 1998a, b). For not differ significantly for most ages; when example, body mass at fledging as a percent- they differed, wild birds were lighter than cap- age of asymptotic adult body mass varies in tive birds. By the end of week 1 captive shorebirds (Scolopacidae and Charadriidae) chicks generally were growing at a faster rate from 53% to 91% (Beintema and Visser than wild chicks for all growth parameters 1989a). In addition, it has been suggested that measured. This trend mirrors results from oth- shorebirds have a higher growth coefficient er studies of precocial birds (Beintema and (K) than other terrestrial, precocial birds Visser 1989a). In most cases, captive and wild (Beintema and Visser 1989b). Of 15 species chicks have similar growth curves, with more reviewed by Beintema and Visser (1989a), K variation in the growth of wild chicks (Visser ranged from 0.05 1 to 0.158, and the inflection and Ricklefs 1993). Faster growth in captivity point (T) ranged from 5.5 to 23.8 d after could be due to an unlimited food supply, hatch. Not surprisingly, body size is positively while slower growth in the wild could be at- correlated with the inflection point and nega- tributed to colder weather, which increases the tively correlated with the growth coefficient. costs of thermoregulation and reduces the That is, larger species reach the half-way point amount of time that chicks can spend forag- in growth at a relatively larger size, and grow ing. A study of time budgets in the field of at a slower rate in proportion to their adult three precocial charadriiform species revealed body size, than do smaller species. Hawaiian that during adverse weather, young chicks Stilts conform to these patterns. were brooded for 75% of the daytime, and as Shape of growth curves-captive Hawai- a result, they could not obtain enough food to ian Stilt chicks grew from approximately 15 satisfy their energy requirements (Beintema g at hatching to 125 g at fledging, attaining and Visser 1989a). In contrast, during good only 60% of adult body mass when they weather conditions, chicks foraged almost fledged. Culmen, tarsus, and wing chord also continuously once they were able to thermo- were still growing at fledging, well below regulate. adult sizes, and did not reach adult values un- Beintema and Visser (1989a, b) hypothe- til after 42 days after hatching. Culmen and sized that for shorebird species, cold temper- tarsus sizes increased rapidly between hatch- atures and cold with rain are the main causes ing and fledging, with culmen growth gener- of slower chick growth in the wild. Specifi- ally following a linear trajectory and tarsus cally, temperatures dropping below 15” C following a slightly sigmoidal pattern. Wing slowed chick growth. In Hawaii, temperatures chord growth was sigmoidal, with slow in coastal wetlands where Hawaiian Stilts growth from hatch day to day 12 followed by breed rarely fall below 21” C, and there are no a substantial increase in growth rate when records of temperatures as low as 15” C. In chicks reached 13-15 days old. addition, rains at coastal areas typically are Mass loss in the first 24-48 h after hatch short-lived. The fact that growth was slower has been reported in some shorebird species in wild chicks despite temperatures above (e.g., Lapwing, Vanellus vanellus; Galbraith 15” C suggests that temperature itself is not 1988) and is attributed to movement away the main factor affecting slower Hawaiian from the nest cup soon after hatching. Al- Stilt chick growth in the field. At warmer tem- though Hawaiian Stilts also leave their nest peratures, Pierce (1986) observed faster cup within a day of hatching, we found no growth in other stilt species. Either a different significant mass loss for captive or wild chicks threshold applies to Hawaiian Stilts or differ- from day of hatch to day 1. Differences in the ences were due to food availability (Beintema distance traveled and the amount of food 1994). available in the first 24 h may explain inter- Comparison to other species.-Hawaiian specific and intraspecific differences in shore- Stilts grow slowly in comparison to other bird mass loss immediately after hatching. shorebirds. Of the 42 growth coefficients Reed et al. l HAWAIIAN STILT CHICK GROWTH 485

Starck and Ricklefs (1998a) reported for 27 Worldwide, stilts average 22-26 days of in- species of shorebird, only 5 were lower than cubation (Johnsgard 1981), which incorpo- what we calculated for Hawaiian Stilts, and rates the Hawaiian Stilts’ incubation length of all came from heavier species. The only pub- 25 days (Colemen 1981). As noted above, the lished estimates of Himantopus growth coef- fledging time is shorter in this species than in ficients are Starcks’ and Ricklefs ’ (1998a) cal- others of its (Johnsgard 1981, Pierce culations from Pierces’ (1986) data on Pied 1986) so there is no extended time as a chick. (Himantopus himantopus leucocephalus) and There are no studies of which we are aware Black (H. novaezealandiae) stilts. These spe- comparing growth rates of precocial species cies have lower adult masses (129 g and 130 across a latitudinal gradient, but it would be g, respectively) than do Hawaiian Stilts, but an interesting assessment. do not fledge until a later age. Hawaiian Stilts Second, the lower growth rate could be a fledge approximately 28 days after hatching; consequence of evolving in an island environ- chicks do not fledge until they are ment where predation rates might have been 34 d, and the fledges even later (at relatively low before human occupancy, and 46 d; Pierce 1986). Similar to the Hawaiian selection for rapid growth might have been Stilt, both species continue to grow after relaxed. Most recorded mortality of adult Ha- fledging. However, based on data presented by waiian Stilts is attributed to introduced species Pierce (1986: fig. 6), Pied and Black stilts (Woodside 1979). However, one would expect fledge at a higher percent of their adult body slower growth to be associated with an older mass. Consequently, despite the longer time age at fledging, which does not occur. In con- to fledging, Pied and Black stilt growth co- trast, the Hawaiian Stilt fledges at a smaller efficients are consistent with expectations percent of adult body mass than do other stilts, based on their adult size (K = 0.175 and 0.129 resulting in an extended post-fledging growth respectively; Starck and Ricklefs 1998a). A K period. of 0.074 would be expected for the 202.5 g Estimating age.-Ideally, estimates of Hawaiian Stilt (Beintema and Visser 1989a), chick age would be based on a trait that but we observed K = 0.065 for Hawaiian changes rapidly and monotonically throughout Stilts in captivity (and possibly lower in the growth. One problem with this method is that field; Fig. 1). Starck and Ricklefs (1998a) also often no one trait is ideal throughout the entire reported faster growth coefficients for the Eu- growth period. Rather, traits differ in their ac- ropean (Recurvirostra avosetta; K = curacy for aging as chicks become older. For 0.213 and 0.171 from two different studies), example, measurements of tarsus and wing which is similar in mass to Hawaiian stilts chord for Hawaiian Stilts are not useful for (168 g and 250 g, respectively). Although the aging chicks at early and late ages because of relationship between body mass and K in their sigmoidal growth patterns. Using mass , is poor (9 = 8%, n = 75 as an indicator of chick age is problematic be- species; Starck and Ricklefs 1998b), these cause it fluctuates rapidly, depending on en- data demonstrate that the slow growth rate ob- vironmental conditions and when chicks are served in Hawaiian Stilts is not a character- weighed in relation to their last feeding. For istic of the . Hawaiian Stilts, culmen length may be the We do not know why Hawaiian Stilts have most useful parameter for aging chicks be- slow growth. The two obvious hypotheses do cause its growth trajectory is fairly linear. Be- not provide satisfactory explanations. First, cause it typically has a constant growth rate growth rate could be correlated with latitude. throughout the chick stage, culmen length has Tropical environments provide a longer breed- been used to age chicks of other shorebird ing season, and growth rates of tropical altri- species in the wild (Beintema and Visser cial species are lower than are those of taxo- 1989a). However, even for traits that tend to nom&ally related temperate species (Ricklefs vary linearly and monotonically throughout 1976, Oniki and Ricklefs 1981). The Hawai- development, there is a tremendous amount of ian Stilt breeding season lasts six months individual variation in daily growth. Unfor- (Coleman 1981). Despite this, neither the in- tunately, this individual variation is magnified cubation nor fledging period is prolonged. bv, measurement error when all measurements 486 THE WILSON BULLETIN . Vol. 111, No. 4, December 1999 are not made by the same person. Thus, de- LITERATURE CITED termination of chick age using body measure- ANTHONY, N. B., D. A. EMMERSON, K. E. NESTOR, W. ments and mass, regardless of the species, L. BACON, P B. SIEGEL, AND E. A. DUNNINGTON. should be viewed as approximate at best. 199 1. Comparison of growth curves of weight se- As a result, we decided to describe general lected populations of turkey, quail, and chickens. plumage patterns for Hawaiian Stilt chicks of Poultry Sci. 70:13-19. known age in the field to set up criteria for BEINTEMA, A. J. 1994. Condition indices for establishing weekly age classes for chicks, de- chicks derived from body-weight and bill-length. Bird Study 41:68-75. fined by the presence or absence of specific BEINTEMA, A. J. AND G. H. VISSER. 1989a. Growth pa- plumage characteristics. The ability to identify rameters on chicks of charadriiform birds. Ardea approximate chick age in the field without 77:169-180. capturing young of this endangered species BEINTEMA, A. J. AND G. H. VISSER. 1989b. The effect could aid in management by helping to iden- of weather on time budgets and development of chicks of meadow birds. Ardea 77: 18 1-192. tify the age at which chicks disappear. To this CLARK, G. A., JR. 1961. Occurrence and timing of egg end, we found definitive differences between teeth in birds. Wilson Bull. 73:268-278. plumage characteristics of specific age classes COLEMAN, R. A. 1981. The reproductive biology of the of Hawaiian Stilts. This should increase abil- Hawaiian subspecies of the Black-necked Stilt, ities to assess survival, the least understood Himantopus mexicanus knudseni. Ph.D. diss., life-history component of this species (Reed Pennsylvania State Univ., State College. COOCH, E. G., D. B. LANK, A. DZUBIN, R. E ROCKWELL, et al. 1998). AND E COOKE. 199 1. Body size variation in Lesser We found plumage characteristics to be use- Snow Geese: environmental plasticity in gosling ful for identifying weekly age classes of Ha- growth rates. Ecology 72503-512. waiian Stilts. Because culmen length is similar EMLEN, S. T, l? H. WREGE, N. J. DEMONG, AND R. E. for captive and wild chicks and has a linear HEGNER. 1991. Flexible growth rates in nestling positive relationship with age throughout de- White-fronted Bee-eaters: a possible adaptation to short-term food shortage. Condor 93591-597. velopment, a combination of culmen length GALBRAITH, H. 1988. Adaptation and constraint in the and plumage description may be the most ac- growth pattern of Lapwing Vanellus vanellus curate way to age wild Hawaiian Stilt chicks. chicks. J. Zool. Lond. 215:537-548. Relying primarily on plumage characteristics, HOLLAND, l? K. AND D. W. YALDEN. 1991. Growth of specifically because they are non-invasive, Common Sandpiper chicks. Wader Study Group and supplementing these observations with Bull. 62:13-15. JOHNSGARD,l? A. 1981. The plovers, sandpipers, and culmen lengths if chicks are captured, will snipes of the world. Univ. of Nebraska Press, Lin- help minimize interference in this endangered coln. species while providing managers with a tool OCONNOR,’ R. J. 1984. Growth and development of for monitoring reproductive success and pop- birds. Wiley, New York. ulation numbers. Because adults and fledg- ONIKI, Y. AND R. E. RICKLEFS. 1981. More growth rates lings differ in plumage patterns, it also will of birds in the humid New World tropics. Ibis 123: 349-354. allow accurate monitoring of reproductive PIERCE, R. J. 1986. Differences in susceptibility to pre- success before molt. dation during nesting between Pied and Black stilts (Himantopus spp.). Auk 103:273-280. ACKNOWLEDGMENTS REED, J. M., C. S. ELPHICK, AND L. W. ORING. 1998. Life-history and viability analysis of the endan- We thank the United States Fish and Wildlife Ser- gered Hawaiian Stilt. Biol. Conserv. 84:34-45. vices’ Pacific Refuges Office, the Hawaii State Divi- REED, J. M. AND L. W. ORING. 1993. Long-term pop- sion of Forestry and Wildlife, and the Marine Corps ulation trends of the endangered Aeo’ (Hawaiian Base Hawaii, Kaneohe Bay for support and use of their Stilt, Himantopus mexicanus knudseni). Trans. facilities, and M. Silbernagle and C. Terry for logistic West. Wild. Sot. 29:54-60. support. This manuscript benefited from reviews by C. RICKLEFS,R. E. 1968. Patterns of growth in birds. Ibis Elphick, N. Warnock, R. Ricklefs, and two anonymous 110:419-451. reviewers. Research was supported by a grant from the RICKLEFS, R. E. 1973. Patterns of growth in birds. II. North Dakota/National Science Foundation EPSCoR Growth rate and mode of development. Ibis 115: to LWO, by National Science Foundation grants DEB 177-200. 9322733 (to J.M.R. and L.W.O.) and DEB 9424375 RICKLEFS, R. E. 1976. Growth rate of birds in the hu- (to L.W.O.), and by the U.S. Dept. of Agriculture. mid New World tropics. Ibis 118:176207. Reed et al. l HAWAIIAN STILT CHICK GROWTH 487

RICKLEFS, R. E. 1983. Avian postnatal development. growth and development: evolution within the al- Avian Biol. 7: l-83. tricial-precocial spectrum (J. M. Starck and R. E. ROBINSON,J. A., J. M. REED, J. I? SKORUPA,AND L. W. Ricklefs, Eds.). Oxford Univ. Press, New York. ORING. In press. Black-necked Stilt (Himantopus THOMPSON,P S., C. MCCARTY, AND W. G. HALE. 1990. mexicanus). In The birds of North America (A. Growth and development of Redshank Tringa to- Poole and E Gill, Eds.). The Academy of Natural tanus chicks on the Ribble saltmarshes, N.W. Eng- Sciences, Philadelphia, Pennsylvania; The Amer- land. Ringing & Migr. 11:57-64. ican Ornithologists’ Union, Washington, D.C. U.S.EW.S. 1985. Hawaiian waterbirds recovery plan. SPSS, INC. 1995. SPSS for Windows. Base system U.S. Fish and Wildl. Serv., Portland, Oregon. VISSER, G. H. AND R. E. RICKLEFS. 1993. Development user’s guide, Release 7.0 ed. SPSS Inc., Chicago, of temperature regulation in shorebirds. Physiol. Illinois. Zool. 66:771-782. STARCK, J. M. AND R. E. RICKLEFS. 1998a. Avian WILSON, S. B. AND A. H. EVANS. 1893. Aves Ha- growth rate data set. Pp. 381-423 in Avian growth waiienses: birds of the Sandwich Islands. Arno and development: evolution within the altricial- Press (1974), New York. precocial spectrum (J. M. Starck and R. E. Rick- WOODSIDE, D. H. 1979. Limited study of nesting by lefs, Eds.). Oxford Univ. Press, New York. stilt on the islands of Maui, Oahu and Kauai. Pro- STARCK, J. M. AND R. E. RICKLEFS. 1998b. Variation, gress Report, Job No. R-III-C, Project No. W-18- constraint, and phylogeny: comparative analysis R-4. Division of Forestry and Wildlife, Honolulu, of variation in growth. Pp. 247-265 in Avian Hawaii.