Table Of ContentWilson Bull., 111(4), 1999, pp. 478-487
GROWTH PATTERNS OF HAWAIIAN STILT CHICKS
MICHAEL REED,' ELIZABETH M. GRAY,^^ DIANNE LEWIS,^
J.
LEWIS W. ORING,3 RICHARD COLEMAN, TIMOTHY BURR,^ AND
^
PETER LUSCOMB^
—
ABSTRACT. We studied chick growth and plumage patterns in the endangered Hawaiian Stilt (Himantopus
mexictmus 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, birds 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 bird that is an endangered subspecies of the
ecology and evolutionary history of different Black-necked Stilt. Like all shorebirds, stilts
species (Ricklefs 1968, 1973, 1983; O’Connor 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 animals (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 Hawaii, breed exclusive-
(USFWS
specific growth patterns can be variable and ly in shallow, lowland wetlands
flexible because of environmental variability 1985), and statewide population counts indi-
and competing selective pressures (Cooch 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
2 Current address; Dept, of Biology, Tufts Univ., —
Medford, MA 02155; E-mail; [email protected] Captive birds. Growth data for captive birds came
’Environmental and Resource Sciences/ 86, 1000 from 15 individuals raised from eggs in 1980 in the
Valley Rd., Univ. of Nevada, Reno, NV 895112-0013. Honolulu Zoo. Because chicks were kept in a common
Current address; USG.S-BRD-PIERC, RO. Box 44, enclosure, some competition for food might have oc-
Hawaii National Park, HI 96718. curred, although food was provided ad libitum. Be-
’ U.S. Fi.sh and Wildlife Service, 91 1 NE 1 1th Ave., cause all birds were subject to the same feeding and
Eastside Federal Complex, Portland. OR 97232. environmental conditions, inter-individual variability
^ 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).
One of the 15 birds was used only for the first 13 d
96815.
Corresponding author. because a bill deformity developed at this time, caus-
**
478
Reed et al. • HAWAIIAN STILT CHICK GROWTH 479
—
ing the individual to lose mass quickly. A sixteenth Fluinage. We considered only tho.se plumage char-
bird was not included in the analysis because of ab- acteristics that were visible in the field: fuzzy appear-
eiTant fluctuations in growth. Its mass at hatch was ance 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 1 1 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 1981), 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 (r^ = 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 (O’Connor 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. Forages
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
W = A X mean values of captive birds. All statistical tests were
two-tailed. Values presented are means ± SD.
W
where 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 1 1 individuals on day
(20W2i.l5dgb).irds —Wild chicks were captured by hand on of hatch (15.7 ± 0.6 g), variability in mass
the islands o.f Oahu, Maui, and Kauai 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 ± 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; « = 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 in = 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
wmeiansgurcehomrednttso otnhe5n5eabriersdts r1a.0ngminmg.inInag1e99f3r,omwehattocohk- 1 (paired t-test: t = —0.432, df = 10, P >
0.05).
ing to fledging using the above methods. During 1993
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
tinhe1c9h9i3c.kWaendaltshoe snoatmeedptehresopnremsaendceeaollr maebasesnucreemoefntans was at 66%, and wing chord length was at
55% (adult measurements from Coleman
egg tooth. Field measurements from 1978-1980 were
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 • Vol. Ill, No. 4, December 1999
LIG. 1. Captive and wild Hawaiian Stilt chick mass and percentage of adult body mass (202.5 g) as a
function of age. Values are means ± SE.
—
ence between mean mass of captive (x = 15.7 Relative growth rates. Relative growth
± 0.6 g) and wild (x = 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 f-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 growt—h 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 1-3. 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 to 17. Mean culmen growth for hand. Specifically, in week 1 chicks are en-
1
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 el al. • HAWAIIAN STILT CHICK GROWTH 481
160i
120
E
E
M 80 a„Eb a
3 Q f
a
(A
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160-
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E
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40-
40 80 120 160
FIG. 2. Growth patterns for wing chord, culmen Mass (g)
length, and tarsus length ofcaptive 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
DISCUSSION
Stilt chicks matched exactly the plumage de-
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
482 THE WILSON BULLETIN • Vol. Ill, No. 4. December 1999
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484 THE WILSON BULLETIN • Vol. Ill, 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 Compa—rison 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 0.051 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 patte—rns. 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, Vcinellus 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. • 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 Stilt’s 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 Starck’s and Ricklefs’ (1998a) cal- others of its genus (Johnsgard 1981, Pierce
culations from Pierce’s (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-
Pied Stilt chicks do not fledge until they are ment where predation rates might have been
34 d, and the Black Stilt 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
A K
respectively; Starck and Ricklefs 1998a). 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 Avocet (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
K
relationship between body m.ass and in their sigmoidal growth patterns. Using mass
Charadriiformes, is poor {H = 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 Recurvirostridae. 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
nomically 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. by measurement error when all measurements
486 THE WILSON BULLETIN • Vol. Ill, 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. StECEL, and E. A. Dunnington.
should be viewed as approximate at best. 1991. 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 wader
chicks derived from body-weight and bill-length.
establishing weekly age classes for chicks, de-
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 77:181-192.
tify the age at which chicks disappear. To this
Clark, G. A., Jr. 1961. Occurrence and timing ofegg
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 ofthe
of Hawaiian Stilts. This should increase abil- Hawaiian subspecies of the Black-necked Stilt,
ities to assess survival, the least understood Himantopus mexicanu.s 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,
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We found plumage characteristics to be use- Snow Geese: environmental plasticity in gosling
ful for identifying weekly age classes of Ha- growth rates. Ecology 72:503-512.
waiian Stilts. Because culmen length is similar Emlen, S. T, P. H. Wrege, N. J. Demong, and R. E.
for captive and wild chicks and has a linear Hegner. 1991. Flexible growth rates in nestling
White-fronted Bee-eaters: a possible adaptation to
positive relationship with age throughout de-
short-term food shortage. Condor 93:591-597.
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 vanellu.s
curate way to age wild Hawaiian Stilt chicks. chicks. J. Zool. Lond. 215:537—548.
Relying primarily on plumage characteristics, Holland, P. 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, P. 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 O’Connor, 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 ofbirds in the humid New World tropics. Ibis 123:
349-354.
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Pierce, R. J. 1986. Differences in susceptibility to pre-
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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.
vice’s 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 Ae’o (Hawaiian
Base Hawaii, Kaneohe Bay for support and use oftheir Stilt, Himantopus mexicanus knudseni). Trans.
facilities, and M. Silbernagle and C. Terry for logistic West. Wild. Soc. 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 1 10:419-451.
reviewers. Research was supported by a grant from the Ricklefs, R. E. 1973. Patterns of growth in birds. 11.
North DakoUi/National Science Foundation EPSCoR Growth rate and mode of development. Ibis 1 15:
to LWO, by National Science Foundation grants DEB 177-200.
9322733 fto 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 118:176-207.
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