Description of Nests, Eggs, and Nestlings of the Endangered Nightingale Reed-Warbler on Saipan, Micronesia

10 Pages·2002·7.5 MB·English

by  Stephen M Mosher

THE WILSON BULLETIN
A QUARTERLY JOURNAL OL ORNITHOLOGY
Published by the Wilson Ornithological Society
VOL. 114, NO. 1 March 2002 PAGES 1-152
Wilson Bull, 114(1), 2002, pp. 1-10
DESCRIPTION OL NESTS, EGGS, AND NESTLINGS OE THE
ENDANGERED NIGHTINGALE REED-WARBLER ON
SAIPAN, MICRONESIA
STEPHEN M. MOSHER* 23,5 ^ND STEVEN G. FANCY'^
—
ABSTRACT. We describe the first verified nests, eggs, and nestlings ofthe Nightingale Reed-Warbler {Ac-
rocephalus luscinia), an endangered species endemic to the Mariana Islands, Micronesia. Nestcomposition, nest
dimensions, and eggs were studied on the island ofSaipan. Nests were located within three habitattypes: upland
introduced tangantangan (Leucaena leucocephala) forest, a native mangrove (Bruguiera gymnorrhiza) wetland,
and a native reed {Phragmites karka) wetland. Nesting substrates included five native and two introduced tree
species and one native reed species. Nests were composed primarily ofdry vine stems, needle-like branchlets
of ironwood {Casuarina equisetifolia), and tangantangan petioles. Nests were compact to bulky in construction
and were secured to a forked arrangement of branches or stems. The background color of eggs ranged from
white to cream to ivory-buff. Eggs were spotted, speckled, and blotched with gray, brown, black, and rust
colored markings. Clutch size was 2-4, with a mode of two. Hatchlings were altricial with closed eyelids and
devoid of natal down with dark gray to black skin. Nestlings examined prior to fledging resembled the adult
plumage, except for the lack of the yellow supercilium found in adults. The nests and eggs have some charac-
teristics similar to those ofother Acrocephaline warblers found throughout Micronesia and Polynesia. Received
29 September2000, accepted 18 March 2002.
The breeding biology of most endemic pas- bier (Acrocephalus luscinia luscinia) on the
serines in the Northern Mariana Islands is island of Saipan is no exception. The lack of
poorly known and the Nightingale Reed-War- reproductive information about the Nightin-
gale Reed-Warbler hinders the development of
' uses Pacific Island Ecosystems Research Center, management practices for conserving this spe-
P.O. Box 44, Hawaii National Park, HI 96718-0044, cies on Saipan. The reasons for this lack of
USA.
vital life history information is, in part, due to
^College of Natural Resources, Fish and Wildlife
Dept., Univ. ofIdaho, Moscow, ID 83844-1136, USA. relatively few field investigations going be-
3Current address: USGS Brown Treesnake Project, yond presence/absence surveys ofbird species
P.O. Box 8255, MOU-3, Dededo, GU 96929-8255, in the Northern Mariana Islands. Some excep-
USA. tions to this were Craig (1989, 1990, 1992),
Currentaddress: USDINational ParkService,Nat- who studied the foraging ecology of Bridled
ural Resource Information Div., 1201 Oak Ridge Dr.,
Suite 200, Fort Collins, CO 80525-5589, USA. White-eyes (Zosterops conspicillatus) and
^Corresponding author; E-mail: [email protected] Golden White-eyes {Cleptornis marchei), as
FRONTISPIECE. Nightingale Reed-Warbler {Acrocephalus luscinia) nestlings at 14 days of age on the
island ofSaipan, Northern Mariana Islands, 11 February 1998. Nest constructed ofdry exotic vine species and
placed in introduced Leucaena leucocephala. Photograph by SMM.
1
2 THE WILSON BULLETIN • Vol. 114, No. 1, March 2002
Urocos
•
*Moug 20’-
Asuncion
0 Agrihon
P Pagon
0Alomogan
-Guguon
Sorigon
.
^Anotahan
MARIANA -Forallon d« Medmillo
ISLANDS
(f Soipan
QTinian
•Aguijan
^
Rota
Cowrrorifcnoith 0* Northern
Moriofto Isiond*
Territory Guom
Guam
0 50 60
Scon(“i60Mi
FIG. 1. Map ofthe Mariana Islands.
well as territoriality and habitat use of Night- The Nightingale Reed-Warbler is a long-
ingale Reed-Warblers, and Stinson and Stin- billed, Old World warbler currently found on
son (1994), who studied breeding ecology of the islands of Saipan, Alamagan, and Aguijan
Golden White-eyes. Of the 16 native forest within the Marianas archipelago (Pratt et al.
bird species found in the Mariana Islands ar- 1987, U.S. Fish and Wildlife Service 1998;
chipelago, only hve have been subjects ofnat- Fig. 1). The reed-warbler has become extinct
ural history or ecological investigations (Rod- on the islands of Guam and Pagan during the
da et al. 1998). latter half of the Twentieth Century (Reichel
Mosherand Fancy • NIGHTINGALE REED-WARBLER ON SAIPAN 3
et al. 1992) and prehistorically on the island We conducted re.search between mid-January 1997
of Tinian (Steadman 1999). The current pop- and mid-July 1998 in the Marpi region, Naftan Pen-
ulation estimate for Nightingale Reed-War- insula, Chalan Lao Lao region, and American Memo-
blers in the Mariana Islands is approximately rsieaalrcPhaersk.ofNkesntowsnearrecehdi-nwgarwblaesrcteornrdituocrtieesdthbryouagchtoiuvte
4,572-4,577 individuals: 1-6 on Aguijan, 346
the year and with the aid ofradio marked birds at the
on Alamagan, and 4,225 on Saipan (U.S. Fish initiation ofthe study. Nests were examined and mea-
and Wildlife Service 1998, Commonwealth of sured after fledging or failure to obtain detailed de-
the Northern Mariana Islands-Div. of Fish scriptions. Eggs were measured and weighed using
and Wildlife 2000). At this time there is no electroniccalipersandaPesolascale.Nestlingdescrip-
information on the breeding ecology of reed- tions were obtained by viewing into the nest with a
warblers on Alamagan and Aguijan. Here we nmeisrtrloirngpsolperiaorndtobfilneodcguilnagr.sWaendredcuorridnegdtmheeabsaunrdeimnegntosf
present the first detailed description of Night- ofmass, unflattened wing chord,exposedculmen, cul-
ingale Reed-Warbler nest structure and com- men, tail length, and tail feather count for nestlings
position, and the first recorded descriptions of prior to fledging.
eggs and nestlings for this species. We also
include additional information on nest sub- RESULTS
strate and placement. Nesting behavior.—A total of 100 reed-
STUDY AREA AND METHODS warbler nests were located on Saipan between
mid-January 1997 and mid-July 1998. We lo-
Saipan (15° 10' N, 145°45' E) is located in thecen- cated 84 nests in upland introduced tangan-
tral region of the 15-island Mariana archipelago. The tangan forest, 15 in a native mangrove wet-
Marianas form a north-south chain of islands about
midway between Japan and New Guinea in the west- land complex and one in a native reed wet-
ern Pacific. Saipan is the second largest island in the land. Fifty-one of these nests were active
Marianas with a land area of 123 km^. The island is when found (four during building, 12 prior to
oflimestone and volcanic origin approximately 22 km egg laying, 26 during incubation, and nine
long and 6 km wide (Fig. 1), with a maximum eleva- during brooding). We found no reed-warblers
tmieoannoft4em7p4erma.tuTrheeocfli2m8a.t3e°iCs.trTohpeicahlumwiidtihtyaniasnnhuiaglh nesting in native limestone forest even when
with monthly means between 79 and 86%. Mean an- their territories included limestone forest frag-
nual rainfall is about 213 cm. Saipan has a dry season ments or were adjacent to limestone forest.
from Decemberto June and a wet season from July to Reed-warblers that inhabited the reed wetland
November (Young 1989). Typhoons can occur during were not found to nest outside ofthe reed bed
any month, but are most frequent from August to De- in the wooded area surrounding the wetland.
cember, with amean ofone typhoon peryearaffecting We observed reed-warblers carrying nesting
the Mariana Islands (Young 1989, Mueller-Dombois
and Fosberg 1998). material into the reed wetland on several oc-
This study focusedonthreehabitattypes utilizedby casions. Juvenile reed-warblers were heard
reed-warblers: upland introduced tangantangan {Leu- making begging calls within the dense reeds,
caena leucocephala) complexes, a tall native reed but no active nests were located.
(Phragmites karka) wetland, and a native mangrove Two peak nesting periods were observed
(Bruguiera gymnorrhiza) wetland. Upland tangantan-
gan habitats were dominated by monotypic stands of during the study, one from January through
tangantangan with no understory, as well as tangan- March and the other from July through Sep-
tangan/sword grass {Miscanthusfloridulus) and/or el- tember. Active nests were located during all
ephant grass (Pennisetum purpureum) mosaics. Some months, except November and December.
stands of tangantangan had a dense understory of in- Twenty-seven ofthe active nests were located
troduced lantana (Lantana camara) and others had during January through March (dry season)
scatterednative shrubs. Thetall reedwetlandconsisted
ofa dense monotypic stand ofPhragmites with a mo- and 20 during July through September (wet
saic of native and introduced tree and shrub species season). This study covered two dry season
surrounding the wetland. The mangrove wetland con- nesting periods and one wet season nesting
sisted of small stands ofmangroves, dense thickets of period. Reed-warblers had a principal nesting
sea-hibiscus {Hibiscus tiliaceus) and rosewood {Thes- area within a given territory, where several
pesiapopulnea), scattered standsoftallironwoodtrees nests from previous nesting attempts some-
(Casuarina equisetifolia), and other native and intro-
ducedtree and shrub species. The amountofundersto- times were found in close proximity to one
ry vegetationvariedthroughoutthemangrovewetland. another. Locating the principal nesting area of
4 THE WILSON BULLETIN • Vol. 114, No. 1, March 2002
TABLE 1. Materials used in Nightingale Reed- The cup lining of nests found in upland tan-
Warbler (Acrocephalus luscinia) nests in two habitats gantangan forest were almost exclusively
on Saipan, 1997-1998. Valuesare numberofnests (%) composed of tangantangan petioles, while
in which the listed material occurred. nests in the mangrove wetland had a larger
amount of ironwood branchlets incorporated
Uplandtangantangan Mangrovewetland
(n = 67nests) (n = 9nests) into the cup lining. Ironwood branchlets were
Material Outer Lining Outer Lining incorporated into the nest structure when iron-
Vines^ 67 (100) 4 (6) 9 (100) 0 (0) wood trees were located nearthe nest site. The
Dry grass blades'’ 15 (22) 1 (1) 1 (11) 0 (0) one nest found in the native reed wetland had
Dry bark strips'’ 15 (22) 0 (0) 1 (11) 0 (0) an outer structure of dry vines, dry coarse
Spider web cas- reed blades, and one spider web casing, and a
ings 7 (10) 0 (0) 0 (0) 0 (0) cup lined with reed panicles.
—
Petioles'’ 4 (6) 66 (99) 0 (0) 2 (22) Nest structure. Nests were of two forms:
Branchlets'' 3 (4) 8 (12) 8 (89) 9 (100) (1) tightly woven compact nests, or (2) larger
TLweiagf^ 11 ((11)) 00 ((00)) 00 ((00)) 00 ((00)) tightly woven nests with bulky outer material.
Nests had open cups that were circular to
^*’MPeonmnoirsdeitcuampchuarrpaunrteiaumanadn/do/rorPausnsikfnloorwanfoseptpi.da. ovoid in shape. In some nests the inner rim
^Leucaenaleucocephala. was tightly woven to form an overhanging lip,
Casuarinaequisetifolia. which may aid in keeping eggs in the nest
during high winds. We measured 66 nests
a reed-warbler pair facilitated future search ef- from among the three habitat types studied.
forts. Outer nest diameter was 106 mm ± 10, 83-
Females gathered nesting material and con- 127 mm (mean ± SD, range), and height was
structed the nest while the male sang from a 90 mm ± 20, 57-177 mm. Cup diameter was
nearby perch. On a few occasions we ob- 65 mm ± 6, 46-86 mm, and cup depth was
served males carrying nesting material to the 45 mm ± 7, 29-58 mm. Rim width at the lip
nest, whereupon the female received and was 20 mm ± 4, 12-28 mm, and rim width
placed the material. One male was observed at base of the cup was 28 mm ± 6, 17-48
attempting to place nesting material into the mm. The nest found in the native reed wetland
nest, but upon unsuccessful placement re- was a loose compact nest with an outer di-
turned to singing from an adjacent perch. We ameter of 1 17 mm, height of 98 mm, cup di-
observed two nests that were constructed di- ameter of 56.5 mm, cup depth of43 mm, rim
rectly on top ofold deteriorating nest material. width at lip of25 mm, and a rim width at base
On three occasions nests in the beginning of 32 mm.
—
stages ofconstruction were dismantled and re- Nest placement. Reed-warblers used sev-
constructed with the same nesting material in en tree species as nesting substrates. In upland
a nearby tree. We never observed a nest used habitat 79 (94%) of the nests were found in
more then once. introduced tangantangan trees, four (5%) in
—
Nest composition. We examined 73 nests native lipstick trees {Ochrosia mariannensis),
to determine the composition ofthe outer nest and one (1%) in an introduced madras thorn
structure and cup lining, including nests from tree {Pithecellobium dulce). We found 15
upland tangantangan forest (/? = 67), a man- nests in the mangrove wetland forest includ-
grove wetland (/? = 9), and a reed wetland (/? ing six (40%) in native ironwood trees, four
= 1). Table 1 summarizes the nesting material (27%) in native sea-hibiscus, three (20%) in
found in nests from upland tangantangan for- mangrove, one (7%) in rosewood, and one in
est and a mangrove wetland forest. Dry vine madras thorn. The nest found in the reed wet-
stems and tendrils of introduced bitter melon land was attached to reed stems. Vegetative
{Momordica charantia) and wild passionfruit cover above, below, and around nests varied
{Passiflora foetida) consistently were the pri- among substrates.
mary component used to form the outer struc- Nest placement within tangantangan con-
ture. The only exception to this was a nest sisted of nests being attached to the main
found in the mangrove wetland, which was stem/trunk and several lateral branches with
constructed entirely of ironwood branchlets. at least one branch supporting the bottom of
Mosheram! Fancy • NIGHTINGALE REED-WARBLER ON SAIPAN 5
FIG. 2. Placement and structure of Nightingale Reed-Warbler {Acrocephahis liiscinia) nests, Saipan, Feb-
ruary 1997 to July 1998. (A) Typical nest placement within introduced Leucaena leiicocephala. (B) Typhoon-
damaged Leucaena leiicocephala trunk with lateral placement ofthe nest. (C) Nest placement in fork ofnative
Ochrosiamariannensis. (D)NestattachedtodroopingbranchofindigenousCasuarinaequisetifolia.Photographs
by SMM.
the nest (Fig. 2a). Some nests located in tan- wood trees were attached to high drooping
gantangan were constructed on the top of ty- branches that extended away from the main
phoon-damaged trunks supported by regrowth trunk (Fig. 2d). The one exception to the
branchlets (Fig. 2b). Nests found in native lip- above placement types was a nest located at
stick trees were supported by the main trunk the terminal end of a lateral branch of a man-
and 3-5 branches that forked from the center grove tree. The nest found in the reed wetland
of the tree (Fig. 2c). Four of six nests in iron- was supported by three vertical reed stems and
6 THE WILSON BULLETIN • Vol 114, No. 1, March 2002
mm
two leaning stems, which supported the bot- size from pinpoints to one that was 2.3
tom of the nest. in diameter (Fig. 3). The depth of the mark-
Nests were securely attached to support ings was variable within the cuticle. Egg sur-
branches/stems with vines either looping face was smooth and nonglossy, with a slight-
around supports or weaving around the sup- ly granular appearance. Mean egg length {n =
port and concealing the support branch/stem 50) was 23 mm ± 1.2, 21.0-25.8 mm and
within the structure of the nest. In all sub- width was 16.9 mm ± 0.5, 15.9-18.0 mm.
strates used for nesting, there always was a Mean egg mass {n = 49, age unknown) was
branch or stem supporting the base ofthe nest. 3.1 g ± 0.5, 2-3.8 g. Clutch size was 2.5 ±
We measured 83 nest trees. Mean nest 0.7, 2-4, with a mode of 2 {n = 20 nests).
height was 4.3 m ± 1.3, 2.3-10.0 m and nest Nestlings.—Nestlings hatched with closed
tree height was 6.1 m ± 3.4, 3.4-25.0 m. Di- eyelids, dark gray to black skin, and totally
ameter (dbh) of nest trees was 60.7 mm ± devoid ofnatal down, with bright yellow gape
59.7, 17.7-318.3 mm. Mean number of sup- flanges. Prior to fledging, nestlings {n = 43)
port branches for 76 nest trees was 3.9 ± 1.2, were almost completely feathered, except
2-8 with a mode of four. Diameter of support around the eyes, ears, chin, and throat (Fig.
branches, including the main stem, was 8.0 4). Plumage was brown on all dorsal surfaces
mm ± 4.6, 1.8-30.5 {n = 282 supports). The with thin buff edges around primaries, sec-
nest found in the reed wetland was 2.2 m high ondaries, and on the tips of the rectrices. The
m
and 0.8 below the tops of the reeds. breast, belly, vent, thighs, and undertail co-
—
Eggs. Eggs were subelliptical and varied verts were light yellow to cream, with the
from dull white to cream to ivory-buff. Eggs flanks brownish yellow to buff. The maxilla
were spotted, speckled, and blotched with ir- was grayish black with broad yellow edges,
regularly shaped markings usually well dis- while the lower mandible was fleshy pinkwith
tributed over the entire shell, commonly with broad yellow edges. Three rictal bristles were
a heavier zone of overlapping markings visible on each side of the mouth above the
around the broader end. Markings were gray, gape flanges. The palate was reddish pink and
brown, black, and rust in color, and ranged in the tongue yellow with two oblong brown
EIG. 3. Nightingale Reed-Warbler (Acrocephalus luscinia) eggs, Saipan, 1998. Photograph by SMM.
Mosherand Fancy • NIGHTINGALE REED-WARBLER ON SAIPAN 7
FIG. 4. Nightingale Reed-Warbler {Acrocephalus luscinia) nestling at day 12, Saipan, 7 October 1997.
Photograph by SMM.
spots just below the tongue spurs. Legs and likely a native reed wetland where reed-war-
toes were grayish blue and foot pads yellow- blers commonly were found by early observ-
ish, with strong well-developed claws black ers on Guam (Baker 1951, Reichel et al.
above and yellowish below. The iris was 1992). Oustalet’s nest measurements were
brownish. The egg tooth was still present on similar to the one nest found during this study
the tip of the bill 2-3 days prior to fledging. in a reed wetland on Saipan. Our Saipan nest
Nestlings lacked the pale yellow supercilium was similar in width to his Guam nest, but
and black lores present in the adult plumage. was 48 mm taller. There was no mention by
We measured 42 nestlings prior to fledging Oustalet of how the nest was placed and se-
at an age ofapproximately 14 ± 2 days. Mean cured. The difference in nesting material
ew2m2xia.pns9ogssmeocmfdho,nrcedusctluwlmliaemnsngesn5w0waw.as3assm1278m1..074.4±mgmm4±.m9,2±.±73,91.-027.54,98,-31m855..m41g,--, fbwlioatudhnedssoinvmeetrhsreeeseGdupbralemaddonemesisnti,antrteuhlseyhSasditrpeyamnsvinanenesdt,sgtmreaamsyss
11.6 mm, and tail length was 13.3 mm ± 4.0, reflect differences in the availability or selec-
4.0-20.5 mm. The mean number oftail feath- toinocneoffounnedstoinngGmuaatemriaalnsd btheetwoeneens tphreesebnitrldys
ers for 41 nestlings was 10.2 ± 0.8, 9-12,
with a mode of 10. on Saipan.
Engbring et al. (1986) described a nest they
DISCUSSION found in 1982 as a large bulky nest ofgrasses.
fouPnrdiorthneesftirdsetscprrieptsiuomnes.d—NMi.ghtAilnfgraeldeMaRrecehde- Ttahnegannesttreweas6 lmocaatbeodveintthheegfrooruknodf. aThteangnaens-t
Warbler nest in June 1887 in a wetland on was not collected because of the presence of
Guam (Oustalet 1895). It was a laterally com- a young fledgling begging near the nest. The
pressed oval cup, with a height of50 mm and nest found by Engbring et al. (1986) fits the
an outer diameter of 120 mm, and was con- nest placement profile of a reed-warbler nest
structed ofrush stems and grass blades rough- in upland tangantangan forest, but their de-
ly woven together. There was no mention of scription that the nest was composed ofgrass-
how the nest was determined to be that of a es does not follow the findings of this study.
reed-warbler. The nest was found in awetland. It is possible the nest was composed primarily
8 THE WILSON BULLETIN • Vol. 114, No. 1, March 2002
of vines that were mistakenly identified as been observed in the Tahitian Reed-Warbler
grasses. (A. caffer), Tuamotu Reed-Warbler (A. aty-
R. J. Craig (unpubl. data) found an empty phus), and the Marquesan Reed-Warbler (A.
nest in 1988 within a known reed-warbler ter- mendanae; Bruner 1974), as well as the Eu-
m
ritory, approximately 4 above the ground ropean Reed-Warbler (A. scirpaceus; Brown
in a 4.6-m tangantangan tree. In a drawing by and Davies 1949). Building and dismantling
Craig (unpubl. data), the nest appears to be newly constructed nests and then rebuilding
attached to upper canopy branches with at them with the same material in a different lo-
least three small diameter support branchlets. cation has been observed frequently in the Eu-
Craig’s drawing of the nest depicts the same ropean Reed-Warbler (Brown and Davies
structure, placement, and attachment in the 1949).
—
fork of a tangantangan tree, as was found in Nest composition. Of the other reed-war-
this study. Craig mentioned that the nest was blers recognized in the Pacific, only the Line
constructed of fine and coarse material with Island Reed-Warbler, Tahitian Reed-Warbler,
strands offibers hanging below the nest, a de- Marquesan Reed-Warbler, and Tuamotu Reed-
piction resembling the appearance of a nest Warbler are known to use vines in the outer
composed ofdmrymvine stems. He estimated the nest structure (Tristram 1883, Holyoak 1973,
nest was 150 in height with an outer di- Bruner 1974). Coconut fibers and grasses are
ameter of 150 mm. His height estimate was the most common nesting materials docu-
wthiethniensttshewreanmgeeasoufrveadr,iabtiuotntwheeofuotuenrdnaesmtondig- mented among eight of the 1 1 other Pacific
mm Island reed-warblers (Tristram 1883, Hartert
ameter was about 23 wider than the larg- 1900, Kirby 1925, Yamashina 1932, Gallagher
est nest we found. — 1960, Williams 1960, Brandt 1962, Holyoak
Nesting behavior We found reed-warblers
. 1973, Bruner 1974, Schreiber 1979, Graves
nested primarily from January through March
1992, Brooke and Hartley 1995, Buden 1996,
and again from July through September. This
Morin et al. 1997). Pacific Island reed-war-
is consistent with prior observations of terri-
blers appear to be generalists in their selection
torial behavior (Craig 1992). Male reed-war- of nesting materials, using the most common
blers are highly territorial and defend territo-
materials available within their respective
ries by singing (Craig 1992). Craig (1992) ob-
habitats.
served an increase in occupied territories dur-
ing January through February and during May The Nightingale Reed-Warbler also is op-
with a subsequent decline in territory occu- portunistic in its use of nesting materials. Dry
pancy by September, which he attributed to a stems of bitter gourd and wild passionfruit
constituted the bulk of nesting material found
decline in breeding activity. Furthermore, sur-
veys conducted by Craig (1996) during Jan- in most nests. These two plant species were
uary and July of 1991 and 1992 revealed an common ground and understory flora within
increase in the number of singing males dur- the three habitat types studied. Neither species
ing those months. of vine is native to the Mariana Islands, with
The small numberofnests found in wetland bitter gourd native to tropical or subtropical
habitats compared to upland tangantangan Asia and Africa and wild passionfruit native
habitat probably does not reflect low densities to tropical America (Whistler 1994).
of reed-warblers, but rather the relative diffi- The reed Phragmites karka is found in fresh
culty in locating reed-warblers and their nests and brackish water marshes and is indigenous
in dense wetland vegetation. Close proximity to the Mariana Islands and the western Pacific
of several nests from a breeding pair’s sepa- (Stemmermann 1981). The only nest that con-
rate attempts also has been observed in other tained a large amount ofgrass blades and pan-
Pacific reed-warblers: Acrocephalus syrinx of icles incorporated into the nest body and cup
the Caroline Islands (Finsch 1881), A. aequin- lining was the nest located in the reed wetland
octialis of the Line Islands (Schreiber 1979) where these two components were abundant.
and A. taiti of Henderson Island (Graves Brown and Davies (1949) found that Euro-
1992). Construction of the nest by the female pean Reed-Warbler used dry Phragmites pan-
with little or no help from the male also has icles almost exclusively for lining nest cups
Mosherand Fancy • NIGHTINGALE REED-WARBLER ON SAIPAN 9
and to a lesser degree in the outer nest struc- vestigations into the breeding biology on the
ture. island of Alamagan in the Mariana Islands
The use of spider webs for securing nests would be another important step toward the
to substrates, as well as for binding nesting future recovery of this species.
materials together is found in a number of
ACKNOWLEDGMENTS
species within the families Tryannidae and
Muscicapidae (Baicich and Harrison 1997).
Funding for field work was provided by the U.S.
However, the function of spider web casings Fish and Wildlife Service and USGS Pacific Island
in the outer structure of Nightingale Reed- Ecosystems Research Center. We thank R. Seman and
Warbler nests is unclear, as they did not ap- S. VogtoftheCommonwealthofthe Northern Mariana
pear to aid in binding nesting material togeth- Islands Div. ofFish and Wildlife and C. Sayon ofthe
er or in securing the nest to the substrate. American Memorial Park (U.S. National Park Service)
GuEagmgsbyandMarnecshtelinigns.—18T8h7e cnoensttaifnoedundthroene fNMo.argCnlhouegsil,sgtriCec.n,suNpJi.psohFriotds.at,eWr,eanNde.spJJ.eociThoanllslloynf,torhMa.tnhkeLiSru.ainBnguvlraulneuh,aabmDl,.e
eggs, but they were not described because field assistance in nest searching and monitoring. We
they were rotten upon reaching their final des- alsothank D. Murray fortranslationofOustalet(1895)
tination (Oustalet 1895). The three-egg clutch and J. Fujimoto for translation of Yamashina (1932).
in Marche’s nest was within the range found J. M. Scottprovidedhelpfulcommentsonearlierdrafts
on Saipan during this study (2-4). The clutch of this paper.
size of the Nightingale Reed-Warbler falls in LITERATURE CITED
the middle among Pacific Island reed-warblers
with one egg in the Cook Islands Reed-War- Baicich, P. J. and C. J. O. Harrison. 1997. A guide
bler (A. kerearako) and up to five in the Hen- to the nests, eggs, and nestlings of North Ameri-
derson Island and Marquesan reed-warblers can birds. Academic Press, San Diego, California.
(Bruner 1974, Holyoak 1980, Brooke and Baker, R. H. 1951. The avifauna of Micronesia, its
origin, evolution, and distribution. Univ. Kansas
Hartley 1995). Publ. Mus. Nat. Hist. 3:1-359.
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