COLONIALITY, MATE RETENTION, AND NEST-SITE CHARACTERISTICS IN THE SEMIPALMATED SANDPIPER

2006·5.1 MB·English

by  Joseph R Jehl

)
The Wilson Journal ofOrnithology 18(4):478—484, 2006
1
COLONIALITY, MATE RETENTION, AND NEST-SITE
CHARACTERISTICS IN THE SEMIPALMATED SANDPIPER
JOSEPH R. JEHL, JR.1
—
ABSTRACT. Coloniality is unusual among Scolopacidae. At Churchill. Manitoba, however, the small, rem-
nant population ofSemipalmated Sandpipers (Calidrispusilla) is highly clumped, with nesting density approx-
imating 3-4 p—airs/ha, and should be considered colonial. The species exhibits high fidelity to territory, mates,
and nest sites behaviors that promote rapid pairformation and allow experienced birds to increase theirrepro-
ductive success by nesting earlierthan pairs forming forthe first time. The value ofexperience andearly nesting
wasevidencedby the factthat sixofsevenreturningyoungwere producedbyexperiencedpairs andhadhatched
on the first day of their respective nesting seasons. Nests were placed in dry locations very near open water.
Those adjacent to small shrubs had slightly greater success, and young produced from these nests had much
higher rates of return than those from nests placed amid sedges. In other parts of their breeding range, Semi-
palmated Sandpipers are also clumped and seem likely to be colonial. If so, estimates ofbreeding populations
derivedfromindirectmethods, suchashabitatassessmentfromaerialphotographs,willhavelimitedapplicability
and will need to be complemented by ground-truthing. Received3 October2005, accepted2 May 2006.
Spatial distribution in breeding birds runs idris mauri) and Broad-billed {Limicola fal-
the gamut from solitary nesting coupled with cinellus sandpipers (Palmer 1967, van Gils
strongly developed territorial behavior to and Wiersma 1996). To this small list may be
highly colonial, with the defended area being added the Semipalmated Sandpiper Calidris
(
limited to the area that parents can protect pusilla), a monogamous and highly territorial
without leaving their nests. Shorebirds (Char- species that breeds in the Subarctic and lower
adrii) exhibit similar variation. Most are soli- latitudes of the North American Arctic. De-
tary nesters, but in some groups (e.g., Dro- spite having been studied in only a few areas,
madidae, Recurvirostridae, Glareolinae) co- its breeding biology is well-documented,
loniality is the rule, the extreme being attained mainly through comprehensive studies at La
by the Banded Stilt (Cladorhynchus leucoce- Perouse Bay, Manitoba, by Gratto-Trevor
phalus), in which densities up to 18 nests/m2 (1992, and references therein). Although
have been reported (Minton et al. 1995. del known to nest at relatively high densities, the
Hoyo et al. 1996, van Gils and Wiersma Semipalmated Sandpiper has not been sus-
1996). Lacking “objective (oreven widely ac- pected of nesting colonially. At Churchill.
cepted) criteria as to how clumped nests must Manitoba, however, that appears to be the
be to constitute a true colony,” ornithologists case. Here I present observations on Semipal-
have used such terms as “semicolonial,” mated Sandpiper spacing and nesting behav-
“strongly clumped,” or “loose colony” to de- ior, along with information on nest-site char-
scribe situations in which “rather more dis- acteristics, philopatry, and other aspects ofthe
persed nests are judged to be in a species' breeding biology that complement
. . . . . .
clump relative to the density of nests in the and extend Gratto-Trevor’s findings.
general vicinity” (Campbell and Lack 1985:
95). In any case, the essence of coloniality is METHODS
that birds ofa feather are disposed to nest near
Observations were made in a potential nest-
each other, the attraction being primarily so-
ciaAlmraotnhegr tShcaonlotpoacaicdaoem.moconlohnaibailtiatty. of any ci2hn0ig0ll4a:rAerae5o8af°”74(,5J0e'0h0Nl.haan9di4n°Lti0hn0e'2“0Wi0m)1m,edmfiraaoptmeinC1hJ9ue9rh3-l
kind is rare, and in the calidridine sandpipers
through 2004 as part of a broader study on
(Calidridini) “semi-coloniality” has been re-
shorebird biology (Jehl and Lin 2001, Jehl
ported or suspected only in the Western (Cal-
2004). From previous studies in 1964 through
1 Smithsonian Ornithology, U.S. National Museum 1967, I was familiar with the status of shore-
of Natural History, Washington D.C. 20560. USA: birds in the Churchill area (Jehl and Smith
e-mail: [email protected] 1970). When I resumed studies in 1991. I
478
)
Jehl • SEMIPALMATED SANDPIPER BIOLOGY 479
failed to encounter Semipalmated Sandpipers (7,000 ha) nesting area occurred in the 25-ha
until 1993, when I found a few pairs nesting meadow described above. Bordered by two
in a small meadow (—25 ha) 25 km east of lakes and dotted with shallow ponds that dried
the Churchill townsite. Then, and in each sub- out by late June, the area was relatively wet
sequent year, I attempted to find all nests and and contained slightly more shrubby vegeta-
mark all individuals. I trapped adults at the tion than some other nearby sites. Because (1
nest in a simple walk-in trap and banded them the nesting area occupied only 3-4 ha of this
with aluminum bands (or stainless steel, when meadow, (2) nest density was extremely high
available) and individually coded colored (see below), (3) similar habitat elsewhere in
plastic bands. I made standard measurements the Churchill area was unused, (4) the historic
with dial calipers (culmen and tarsus to 0.1 distribution of Semipalmated Sandpipers at
mm; flattened wing to 1 mm) and weighed Churchill had not been limited to this type of
each bird on a digital scale (to 0.1 g). Chicks habitat, and (5) nesting areas used through the
were banded (but not color-marked) before 1960s, though largely unchanged, were no
they left the nest. From this effort, the iden- longer used, it was clear that the birds were
tities of most adults (88% of 93 from 1993 to attracted to each other and not to any specific
2001) and young (73% of 120 from 1993 to habitat or topographic conditions. Conse-
2000) were known, which allowed their sta- quently, their nesting behavior could be de-
tus, mates, distribution, and nesting success to scribed as colonial. Elsewhere in the Churchill
be followed from year to year. I aged adults area, I encountered Semipalmated Sandpipers
on the basis of Gratto and Morrison’s (1981) only twice from 1993 through 2004: one un-
observation that most first-year birds are dis- mated male, and an apparent pair, each located
tinguishable from older birds by having up to >5 km from the colony. All three birds dis-
four newly replaced outer primaries. Obser- appeared after a few days.
vations in 2001 through 2004 focused on doc- The colony contained five pairs in 1993.
umenting the identities of returned birds. Colony size had increased slightly by 1995
In most calidridines, males are typically (11 nests; Table 1) and (probably) 1996, but
smaller (e.g., Jehl and Murray 1985), but there runoff in 1996 flooded some early nests and
is much overlap. To determine sex, I also used may have prevented some pairs from finding
behavioral information, including observa- suitable territories or renesting. In 1997, the
tions that males defend territories much more number of adults was halved and I found only
strongly, sing longerand more complex songs, two nests. Subsequently, through 2001, the
and are bolder around the nest. For birds re- colony size fluctuated from two to three pairs,
turning in subsequent years, it was usually and by 2003 (and perhaps 2004) there was
possible to use behavior to test earlier deter- only a single, unpaired male. At maximum
minations: in only 2 of25 cases did a tentative size in 1995 (Fig. 1), the colony encompassed
sexing need to be reconsidered. 3.4 ha (determined by a polygon drawn
around the outermost nests; this area included
RESULTS
open-water areas where nesting was impossi-
—
Phenology and colony designation. Semi- ble), had a maximum linear extent of 416 m,
palmated Sandpipers migrate through the and a density of 3.2 pairs/ha (maximum = 4.1
Churchill region between the last days ofMay in 1993). Nests were tightly packed, the near-
m
and the first third of June. Locally nesting est-neighbor distance averaging about 55
birds move immediately to breeding areas, (minimum = 31 m).
—
where they engage in prolonged and conspic- Matefidelity. -As in some othercalidridines
uous territorial and courtship displays. Dis- (e.g., Least Sandpiper, Calidris minutilla\ Stilt
play flights take place at elevations of 40-50 Sandpiper, C. himantopus Dunlin, C. alpina\
m and may last 10 min or more. Typically, Jehl 1970; JRJ unpubl. da;ta), Semipalmated
these displays involve several birds, which Sandpipers form long-term bonds and pairs
chase back and forth over, and well beyond, tend to re-occupy former territories as long as
the nesting area. both members are alive (see also Gratto et al.
From 1993 through 2004, the only Semi- 1985). In 16 cases in this study, both partners
palmated Sandpipers nesting in the potential returned, pairs reunited 13 times in the follow-
480 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 118, No. 4, December2006
TABLE 1. Population size and density ofSemipalmated Sandpipers at Churchill, Manitoba, 1993-2001.
Nestingarea Maximumextent Distancetonearestnest(s):
Year Populationsize3 No.nests (ha)c No.pairs/hac ofcolony(m) [range]andmedian(m)
1993 >10 5 1.2 4.1 126 [54-181] 87.3
1994 16-19 8 2.8 2.9 268 [52-63] 55.1
1995 22-24 11 3.4 3.2 416 [31-101] 54.4
1996 21-22 8b 2—.7 2—.9 381 [37-124] 88.4
1997 12 2 — — 121 121
1998 7 3 — — 2—74 [84-193]
1999 4 2 — — — 55
2000 6-8 3 — — — —90, 91
2001 >6 3
aEstimatednumberofadultsincolonyearlyintheseason.
bOmitsonerenesting.
cCouldnotbecalculatedfromtwopointsorwhennestswerearrangedlinearly.
ing season, and all had nested successfully in the other pair acquired new partners, but the
the previous year. Three pairs divorced (one males retained their previous nest sites. Ofthe
previously successful, two unsuccessful). The pairs that reunited, two remained intact for
successful male acquired a new mate and his four seasons, three for three seasons, and two
old mate soon disappeared. Of the two pre- for two seasons.
viously unsuccessful pairs, the nest ofone was Nineteen pairs failed to reunite. Thereasons
flooded, the female acquired a new mate, and can only be guessed, as banded but unidenti-
the old male skipped breeding; both birds of fied birds occasionally showed up early in the
FIG. 1. Location and spacing ofSemipalmated Sandpiper nests (•) at Churchill, Manitoba, 1995.
—
x n n
Jehl • SEMIPALMATED SANDPIPER BIOLOGY 481
TABLE 2. Spacing and dispersal ofSemipalmated Sandpipers at Churchill and La Perouse Bay, Manitoba.
Churchill 1993-2001 LaPerouseBay 1980-19843
Variable n Spacing,behavior n Spacing,behavior
Size ofbreeding area; habitat 3-4 ha; a single small 2 km2 on delta ofMast
;
meadow River
Population size; density 2-11 pairs; 3-4/ha 100 pairs; 1/ha
Pairs reuniting, ifboth alive 16 13 (81%) 79 64 (81%)
Reuse ofold nest cup 41 8 (19.5%) 305 13 (4.3%)
Rate ofnest reuse ifboth 13 8 (61.5%) No data
parents returned
Nest shift: reunited pairs 14 Range = 0-85 m; mean = 168 Range = 0-575 m; annual
25.4 ± 36 m; mode = 0 m medians: 40-66 m
Nest shift: female mate change 8 4-360 m, mean = 153 ± 33 Range = 23-825 m; annual
126 m; median = 115m medians: 138-174 m
aFromGrattoetal.(1985).
year and then disappeared, perhaps without the greater desirability ofshrub sites was clear
mating or perhaps because their nest was lost from their retention rates. Of 25 successful
before I could find it. In several cases, the shrub sites, 14 (56%) were reused, 13 by a
break-up was evidently due to bad timing (one returning pair and 1 by a male with a new
partner returned late) or the unavailability of mate. Of the 11 successful shrub sites that
a previous nest site (see below). were not reused, the nest cup or habitat had
Nest-site selection and site tenacity.—Just become unusable {n = 3) orone orboth mates
as Semipalmated Sandpipers tend to retain failed to return ( = 8). In sedge sites, 8 of
mates and territories from year to year, they 11 nestings were successful, yet none was re-
also retain nest sites, as long as the previous occupied (1 site was used several years later
nesting attempt was successful, the mate re- by a pair with no previous breeding experi-
mains alive, and the nest is in suitable con- ence; the nest failed). In the other cases, the
dition and does not contain unhatched eggs habitat had changed over the intervening win-
from the previous season. Of 13 cases in ter ( = 3) or one or both mates failed to
which both mates returned and reunited, the return (n - 4).
distance to subsequent nests ranged from 0 to Among individuals that moved to a new lo-
85 m (mode = 0 m; Table 2). One pair used cation, males {n = 9) tended to stay near their
the same nest for 4 successive years. previous nest site (median distance == 40 m).
Semipalmated Sandpipers selected nest lo- Eight paired with females thathad no previous
cations very near ponds (mean = 10.9 m ± experience, and one bred successfully in the
8.8, range = 0.5-29.5 m, n = 26), but placed same territory for 4 successive years, each
their nests in dry situations on the sides or time with a new mate and each time moving
tops of small hummocks or ridges. Two types —50 m away from the previous site before
of nest sites were used: “shrub” sites were returning to the original nest in the 4th year.
located under, or adjacent to, small bushes Females {n = 8) tended to move farther away
in this case sweetga—le {Myrica gale) or dwarf from previous nest sites (median = 115 m).
birch (Betula nana) which typically allowed Three females paired with experienced males
access from only one direction; “sedge” sites that held territories near the center of the col-
were in low, damp areas andnests wereplaced ony; one ofthese birds failed to nest one year
in a clump of sedge {Care spp.). At 41 doc- when her nest was flooded, but she returned
umented sites (including those reused by the to her old territory (by then held by adifferent
same pair in subsequent years), 30 were in male) and nested within 4 m of the original
shrub and 11 in sedge. Nesting success was scrape. The other five females bred with in-
slightly (but not significantly) greater in shrub experienced males, whose nests in all but one
sites (83% versus 72%), which are better con- case were on the periphery ofthe colony. One
cealed and less subject to flooding. However, pair in its 2nd year moved 60 m, then 80 m
-
482 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 118, No. 4, December2006
—
in year 3, and 80 m again in year4. When the birds typically have greater success than
nest was flooded in year 4, the birds moved those that start later (e.g., Soikkeli 1967, Jehl
m
85 m, which brought them to within 4 of 1970, Gratto et al. 1983, Black 1996, Handel
their original nest. and Gill 2000, Ruthrauff and McCaffery
Of 120 local chicks banded, 7 returned to 2005). Early breeding is enhanced by high
breed. At least six of these were produced by rates ofterritory, mate, and nest-site retention,
pairs in which at least one parent had nested which allow mates to begin nesting as soon
successfully in a previous year; five (including as habitat conditions permit. These behaviors
two from the same clutch) were produced by are especially important where breeding sea-
two pairs. All returning young paired with in- sons are short, so it is not surprising that they
experienced mates; the males (n = 5) moved have been reported in a variety of shorebirds
130-225 m (mean = 197 m) and the females that nest in the Arctic, including Dunlin, Least
(n = 2) moved 85 and 226 m from their natal and Stilt sandpipers, and Black Turnstone (Ar
sites. When the colony was relatively large, enaria melanocephala; Soikkeli 1967; Jehl
young males, with one exception, were only 1970, 1973; Gratto et al. 1985; Jonsson 1987;
able to obtain territories at the colony edge. Handel and Gill 2000; Sandercock et al. 2005;
One bred on the periphery in his 1st year and JRJ unpubl. data). In this study the importance
then moved to a more central site in his 2nd ofadult experience and early nesting was con-
year. Another male obtained a central location firmed by the observation that six ofthe seven
at first breeding, but only after experienced chicks that returned to nest were not only pro-
neighbors had reduced territory defense (cf. duced by experienced parents but also hatched
Jehl 1973) and started incubating; its young on the 1st day oftheir respective hatching pe-
hatched a week later than those ofother pairs. riods. The one exception hatched from the
penultimate nest of its season and was pro-
DISCUSSION
duced by a pair that had not nested together
—
Breeding behavior The aspects of mate previously. Although the female had no
.
and territory retention, philopatry, and dis- known experience, the male had bred suc-
persal treated in this study largely conform to cessfully twice. Whereas the experience of
those reported by Gratto et al. (1985) at La both parents is surely relevant, that of the
Perouse Bay, —30 km to the east (Table 2). male is paramount because in this species and
At Churchill, nest density was greater than it many other sandpipers, he takes the sole or
was at La Perouse Bay (3-4 versus 1 pair/ha), major role in rearing the chicks from hatching
returning pairs dispersed much less (if at all) to fledging (Jehl 1973, Gratto-Trevor 1991;
from previous nests, and reuse ofthe nest cup JRJ unpubl. data).
—
was greater (19.5% versus 4.3%; 61.5% [this Territoryfunction and spacing. When not
study] if both pair members returned). These incubating, Semipalmated Sandpipers left
differences were probably related to topogra- their territories and departed the colony area.
phy and the size and stability ofthe respective Some moved to the mudflats of Hudson Bay,
nesting areas. Churchill birds were restricted a minimum distance of2-3 km, whereas when
to a small meadow, whereas Semipalmated water levels were low inland, several might
Sandpipers at La Perouse Bay bred on a river have fed together on mudflats in a lake bor-
delta that often experienced high flows during dering the colony. Because territory in this
runoff, resulting in greater loss of old nest species is not based on food availability, it
cups. At Churchill, young males tended to appears that nest spacing is determined by a
breed at the colony’s edge but did not disperse balance between attraction to conspecifics and
as far from their natal sites as they did at La the need to maintain sufficient distance be-
Perouse Bay (197 m versus 549 m, respec- tween neighbors to prevent predators from
tively), probably because the colony was finding nests. —
much smaller. Density and population estimates. Semi-
For any species, the timing of breeding is palmated Sandpipers are reported to nest at
critical to reproductive success (Lack 1968), greater densities than other sandpipers, except
and it is widely—acknowledged that individuals perhaps the Western Sandpiper. On the North
nesting earlier nearly always experienced Slope of Alaska, where the Semipalmated
Jehl • SEMIPALMATED SANDPIPER BIOLOGY 483
Sandpiper is abundant. Cotter and Andres 1983. Nestingsuccessofyearlingandolderbreed-
(2000) reported mean densities of 30 pairs/ ers in the Semipalmated Sandpiper Calidris pus-
km2 farther inland they noted up to 21.3 ilia. Canadian Journal ofZoology 62:1889-1892.
nest;s/km2 At La Perouse Bay, Manitoba, Gratto, C. L. and R. I. G. Morrison. 1981. Partial
. postjuvenal molt of the Semipalmated Sandpiper
Gratto et al. (1985) estimated territory size to (Calidris pusilla). Wader Study Group Bulletin
be 1.0 ha, including defended water areas 33:33-37.
(maximum density was 2.3 pairs/ha, based on Gratto, C. L., R. I. G. Morrison, and F. Cooke.
dry land areas). At Churchill, density was 1985. Philopatry, site tenacity, and mate fidelity
even greater, reaching up to 4 pairs/ha (= 400 in the Semipalmated Sandpiper. Auk 102:16-24.
pairs/km2, inclusive of pond areas). While all GratSteom-iTpraelvmoart,edC.SanL.dpi1p9e9r1.CaPlairdernitsalpuscialrlea ibnrotohde
populations of Semipalmated Sandpipers do desertion by females. Ibis 133:394-399. :
not necessarily have the same nesting habits Gratto-Trevor, C. L. 1992. SemipalmatedSandpiper
(e.g., Gratto and Cooke 1987), spacing is also (Calidris pusilla). The Birds of North America,
clumped in the three breeding localities clos- no. 6.
est to Churchill: Gordon Point and Fox Island Gratto-Trevor, C. L. 1996. Use ofLandsat TM im-
(Jehl 2004; JRJ unpubl. data) and La Perouse agery in determining important shorebird habitat
in the Outer Mackenzie Delta, Northwest Terri-
Bay (C. Gratto-Trevor pers. comm.). This and tories. Arctic 49:11-22.
the high densities reported elsewhere suggest Handel, C. M. and R. E. Gill, Jr. 2000. Mate fidelity
that the species is probably colonial through- and breeding site tenacity in amonogamous sand-
out its range. If so, estimates ofbreeding pop- piper, the BlackTurnstone. Animal Behaviour60:
ulations derived from indirect methods, such 471-481.
as habitat assessment from satellite photogra- Jehl, J. R., Jr. 1970. Sexual selection for size differ-
ences in two species ofsandpipers. Evolution 24:
phy or vegetation maps (e.g., Gratto-Trevor 311-319.
1996), will have limited applicability. Addi- Jehl, J. R., Jr. 1973. Breeding biology and systematic
tional documentation of the kinds ofbreeding relationships of the Stilt Sandpiper. Wilson Bul-
behavior reported in this paper, complemented letin 85:115-147.
by ground-truthing ofnest spacing in different Jehl, J. R., Jr. 2004. Birdlife ofthe Churchill region.
geographic regions, will be useful. Trafford Press, Victoria, British Columbia.
Jehl, J. R., Jr., and W. Lin. 2001. Population status
ACKNOWLEDGMENTS of shorebirds nesting at Churchill, Manitoba. Ca-
nadian Field-Naturalist 1 15:487-494.
I was assisted in the field by J. Klima, W. Lin, J. Jehl, J. R., Jr., and B. G. Murray, Jr. 1985. The
Terp, C. MacDonald, and many volunteers associated evolution of normal and reversed sexual size di-
with the Churchill Northern Studies Centre. S. I. Bond morphism in shorebirds and other birds. Current
prepared the map in Figure 1 and helped compile the Ornithology 3:1-86.
data. I am grateful to C. Gratto-Trevor for laying the Jehl, J. R., Jr., and B. A. Smith. 1970. Birds of the
groundwork for this study and to her, J. Klima, A. Churchill region, Manitoba. Special Publication
Henry, and R. I. G. Morrison for insightful comments no. 1, Manitoba Museum of Man and Nature,
on this manuscript. Winnipeg, Manitoba.
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