Condor, 81:4041108 0 The Cooper OrnithologicalSociety 1979

NATURAL HISTORY OF THE

J. MARK JENKINS

The (RaZZus owstoni) is a flight- tats. Since 1961, counts have been conducted at dawn less , endemic to Guam of the Mar- from vehicles moving between 20-30 kph, first weekly iana Islands. Little has been published on and later bimonthly. In addition, roadside counts dur- ing 1968 recorded the number of rails seen in four dif- this rail except Bakers’ (1951) brief notes, ferent types: savanna, mowed grass with brush, Perezs’ (1968) note on breeding seasons, mature mixed forest, and mixed woodland with brush. Kiblers’ (1950) description of the call note, Total numbers of rails and rail broods observed month- and Carpenter and Staffords’ (1970) work on ly and yearly were converted to rail and rail broods per 160 km of travel. its salt glands. Lint (1968) published a pop- Food habits were determined by examining gizzards ular article on the Guam Rail containing lit- and proventriculi, primarily from road-killed individ- tle biological information. A study of the uals (N = 34). The degree of digestion of stomach con- biology of the species appears especially tents often limited the specific identification of food appropriate in light of numerous recent ex- items. Weights and measurements were obtained from specimens collected during the early 1960s’ and from tinctions of flightless rails from oceanic is- road-killed in good condition. lands (Ripley 1977), and current declines in Guam Rail populations. RESULTS AND DISCUSSION Systematists have variously interpreted GENERAL DESCRIPTION phylogenetic affinities of R. owstoni. Olsen RaZZus owstoni is a large rail with dark (1973) reclassified R. owstoni into the ge- brown head, neck, back, rump, tail, legs, nus GaZZiruZZus. Ripley (1977) questioned feet, and bill. The wings, lower breast, ab- this classification and continued to place the domen and under tail coverts are barred Guam Rail in the genus RaZZus; that no- black and white, while extensive areas of menclature is used herein. Generally, R. ash gray occur on the neck, upper breast, owstoni is believed to have colonized and in a superciliary stripe (Fig. 1). Plum- Guam through the Philippines from stock ages of the sexes are similar (Mayr 1945, probably resembling the Banded Land-Rail Baker 1951). As in other RaZZus, the body is (R. philippensis; Baker 1951, Olsen 1973) or elongated and laterally compressed, partic- the (R. torquatus; Ripley 1977). ularly in the neck and breast regions, allow- Since 1960, staff biologists of the Guam ing the birds to move rapidly through dense Division of Aquatic and Wildlife Resources . Males are larger than females have collected field notes on the Guam Rail (Table 1); the sexes often are distinguish- and monitored population sizes through able by their sizes when seen together in roadside counts. These data form the basis the field. for the present paper. DAILY ACTIVITIES STUDY AREA The Guam Rail is a monogamous territorial Guam is the largest and southernmost island of the species. The sizes of daily or seasonal Marianas Archipelago. Lying at approximately 13” 13N,’ 145”E, Guam is 45 km long, 6 to 13 km wide, ranges are unknown. Recorded incidents of and has a uniformly warm and humid climate through- fighting, presumably between males, prob- out the year. Rainfall is heaviest from July through ably are related to territoriality. November, with an average annual rainfall of 219.6 cm. These birds are often seen during the ear- Guam is divided into a northern half, a limestone pla- teau or “mesa” with coralline limestone soils predom- ly morning and late evening when they ven- inating, and a southern half which is primarily volcanic ture from cover to forage and bathe along in origin, with laterite soils. Stone (1970) described the field edges and roadsides. They also forage predominant vegetation of the northern plateau as “ty- at night, a trait considered common among phoon forest” and recognized seven subtypes, includ- RaZZus species (Ripley 1977). The Guam ing Pandanus forest and holophytic-xerophytic scrub forest, widely used by the Guam Rail. Dominant vege- Rail is wary, seldom wandering far from the tation on the southern volcanic soils includes ravine shrub growth to which it retreats when forest and savanna. alarmed. Though capable of short bursts of flight of l-2 m, the seldom flies. METHODS Nothing is known of the rails’ behavior Roadside counts of 40.8 km and 39 km were conducted when under cover, but in open areas it de- over northern and southern Guam, respectively. The votes much time to care. Bathing northern route encompassed primarily mixed wood- land and second growth , while the southern and preening occupied 35% of 113 min of route covered savanna and mature ravine forest habi- observation of 26 rails. Birds frequently

14041 THE GUAM RAIL 405

sects, particularly butterflies. They first lo- cate a prey item while standing still and then attempt capture with a quick burst of speed. Baldwin (1947) observed similar be- havior in the now extinct Rail (Por- xanula palmeri). R. owstoni obtain seeds and flowers from low grasses and shrubs. They can stretch their bodies nearly per- pendicularly, reaching food 40 cm or more above ground. Adult rails may locate specific foraging spots and allow their chicks to peck there, often moving away and permitting the ju- FIGURE 1. The head of a Guam Rail. veniles to forage independently. Alternate- ly, adults may secure food (usually ) and then allow the chicks to peck the items preen or bathe in small puddles along se- from their bills, or they may lay them in cluded roadsides following early morning front of the chicks. rain showers. FOOD HABITAT PREFERENCES owstoni apparently prefer The Guam Rail formerly occurred in most over vegetable foods (Table 3). The exten- habitats on Guam. Table 2 shows the mean sive use of gastropods, particularly snails, is number of rails observed per 160 km of trav- probably related to the accidental introduc- el in four habitat types in 1968. Mowed tion in 1945 of the giant African snail (Acha- grass with brush habitats included main- tina fulica). Believed introduced from a tained areas of mowed grass along road- ship at commercial port, the African snail sides, telephone lines and antenna fields, rapidly expanded its range into most habi- bordering scrub communities. The number tats on the island and has become an im- of rails recorded in the mature mixed forest portant food for the rail. The birds also have habitat is likely an overestimate as a result been observed eating carrion and geckos of roadside censuses being conducted along (Hemidactylus frenatus), although these the edge of these habitats, where rails were items were not found in the 34 stomachs abundant. Rails are seldom seen or heard in examined. Insects, representing at least the interior of the mature limestone forest, three orders (Othoptera, Dermaptera, Lep- and this habitat is best considered marginal idoptera), are important in the Guam Rail for the species, as are savanna habitats oc- diet. curring in southern Guam (Table 2). The Vegetable foods included unidentified species does not occur in the freshwater seeds and palm leaves. During the dry sea- habitats of Guam. son rails have been reported to damage crops such as cucumbers, tomatoes, and var- FORAGING BEHAVIOR ious melons, though such damage probably Guam Rails most frequently peck food results from the birds ’ securing moisture items directly from the ground. This tech- rather than food. nique is of primary importance in securing Snail shells, or their pieces, may be in- snails and slugs, especially following rain gested in the course of feeding, but also ap- showers. Birds also “hawk” low flying in- pear to function as grit. Coral chips ranging

TABLE 1. Body measurements (mm) and weights (g) of male and female Guam Rails.

Wing Tail Culmen Tarsus Weight Male Mean 124.8 51.7 39.0 52.1 241.4 Range 120-133 50-53 33-43 50-56 174.0-303.0 N 6 3 6 4 27 Female Mean 119.2 47.6 38.1 47.0 211.9 Range 122-125 45-52 3442 43-54 170.0-274.2 N 7 5 7 6 20 406 J. MARK JENKINS

TABLE 2. Number of Guam Rails recorded in four TABLE 3. Stomach contents of 34 Guam Rails. habitat types during 1968 on roadside counts totaling over 800 km. Number of times Percent occurring in occurrence in P&y; 34 stomachs 34 stomachs Habitat type Number (%) Snails 22 64.7 Savanna 2(1.0) 1.6 Slugs 4 11.8 65.3 Mowed grass with brush 83 (40.1) Insects 13 38.2 43.8 Mature mixed forest 54 (26.1) Vegetable matter 4 11.8 56.2 Mixed woodland with brush 68 (32.8) Coral chips (grit) 14 41.2 Total 207 Snail shells (grit) 12 35.3

in diameter from I-9 mm are eaten specif- YOUNG ically as grit; eight chips were the maximum The hatch asynchronously and the number found in one gizzard. young are highly precocial, leaving the nest within 24 h after hatching. The eggshells NESTING are consumed by an adult, presumably the Guam Rails nest on the ground, both sexes female. Brood nests, which have been ob- sharing in the construction of a shallow nest served in other rails, have not been reported of interwoven loose and rooted grasses. One for R. owstoni. nest measured 13 cm in diameter and 3 cm Guam Rail broods range from one to four deep. The eggs are white to pinkish with chicks, with two being the mean and me- small spots of pink or blue concentrated at dian size. In 172 broods, there were 54 with the large ends. Nine eggs averaged 39 mm one chick, 77 with two, 35 with three, and (3741) in length and 29.3 mm (28-30) in 6 with four chicks. Both sexes brood the width. young. The typical consists of 34 eggs, One female chick was raised in captivity representing a smaller clutch size than con- and was weighed daily. At one week, it generic species in the north temperate re- weighed 38.6 g, two weeks 75.2 g, three gions (Baldwin 1947). I interpret the small weeks 122.2 g, four weeks 135.3 g, five clutch size of the Guam Rail as being an weeks 175.1 g, six ,veeks 195.2 g, seven evolutionary result of year-round breeding weeks 211.3 g, and eight weeks 205.8 g. The in a formerly predator-free, tropical envi- young bird was covered with black natal ronment. One clutch hatched at 19 days. down through its first three weeks, gradu- Both sexes share in the incubation duties. ally developing juvenile contour It is suspected that renesting occurs, but the during the fourth week. Feathers on the number of clutches per year is unknown. ventral and crural pterylae developed rap- Although the species nests year-round, idly, giving the chick a noticeable ventral Perez (1968) suggested the existence of a barring by the end of the fourth week. Be- peak breeding period during the rainy sea- tween the fourth and sixteenth week of life, son from July through November, based on birds in the juvenal plumage are identifi- the average number of rail broods seen per able by the less extensive areas of gray on month on weekly roadside counts (Fig. 2). the neck, breast and superciliary stripe. These data probably do indicate an increase Thereafter, first-year birds are indistin- in nesting activities during rainy months. guishable from adults in the field. The age However, if a peak nesting period does ex- at sexual maturity is unknown, as is the lon- ist, it probably is not of the magnitude sug- gevity of the species, although one of ten gested in Fig. 2 because adult rails also are Guam Rails sent to the San Diego in more frequently observed then. Since adult 1968 is over 11 years old. rails are more visible during this period, it is not surprising that broods also are more POPULATION AND DISTRIBUTION visible, as chicks closely follow adults. I in- Rail populations have fluctuated consider- terpret these data as indicating a behavioral ably since the beginning of roadside counts characteristic of R. owstoni in response to over northern and southern Guam in 1961 increased food items, principally snails and (Fig. 3). The increase of rails during the slugs, in open areas during the rainy season, 1960s’ may be related to the introduction of while not discounting increased nesting ac- the giant African snail, particularly on the tivity at the same time. northern plateau. Recently, the species has THE GUAM RAIL 407

FIGURE 2. Mean number of Guam Rails and broods seen monthly per 160 km of travel on north and south FIGURE 3. Mean number of Guam Rails seen yearly routes and mean monthly rainfall for years 1961-1975. per 160 km of travel from 1961 to 1978 on north route and from 1961 to 1975 on south route. severely reduced its range, virtually disap- pearing from southern Guam and the cen- would require some evidence that preda- tral portion of the northern plateau, becom- tion has increased over the past decade, ing localized in small areas around the since all predators were present on Guam fringes of the plateau. during the relatively high rail populations Causes for this decline in populations are of the 1960s.’ No data are available on past uncertain. However, circumstantial data or present predator populations. suggest that pesticide poisoning may be in- Habitat destruction probably has not volved. These data include: 1) the fact that been a major factor in rail declines of the DDT was dusted on Guam weekly by U.S. 1970s.’ Development has occurred primar- military units during and following World ily in northern and central Guam and it is War II, with the use of pesticides continu- difficult on this basis to explain the disap- ing by the military, developers, and by local pearance of the rail from its southern habi- farmers, 2) the findings that a native species, tats. Habitat destruction cannot be over- the Vanikoro Swiftlet (Collocallia vaniko- looked as a future detriment to the species rensis), tested in 1975 contained body tissue in its northern range, as areas of localized concentrations of DDE averaging 0.27 ppm rail populations are under increasing pres- (0.17-0.39), and 3) the virtual disappearance sure from development. of the entire native avifauna from the south- Conservation measures initiated for R. ern half of Guam, combined with the fact owstoni include a proposal by the Govern- that southern Guam with its and ment of Guam to add the species to the U.S. streams received heaviest pesticide appli- List, with designation cations. of appropriate critical habitats. Studies are , by a number of introduced being undertaken to determine precise predators, cannot be discounted as a possi- causes for declining rail populations. Should ble factor in declining rail populations. Nest present declines continue, the southeastern predation by the Philippine snake (Boi- portion of the northern plateau encompass- ga irregularis), monitor lizard (Varanus in- ing a contiguous portion of federal lands, dicus), three species of introduced (Rat- including Mangilao Communication and tus norvegicus, R. rattus, R. exulans), as Marbo Annexes of Andersen Air Force well as feral dogs, and may affect Base, and the U.S. Naval Golf Course and the reproduction of the Guam Rail. Yet for Communication Station, may represent the this to be a major factor in recent declines best opportunity for maintaining a wild pop- 408 J. MARK JENKINS

ulation of these birds. All use of pesticides lowing former staff biologists who contributed field and herbicides should be discontinued in notes for this paper: Terry A. McGowan, Maurice H. this area, combined with a sustained effort Taylor, Alan Courtwright, Nick Drahos, Jack Jeffrey, and Gerald S. A. Perez, who also reviewed the manu- at predator control. The success of these and script. The conservation officers of the Government of future conservation measures may well de- Guam conducted many of the roadside counts. termine the continued existence of the Guam Rail. LITERATURE CITED SUMMARY BAKER, R. H. 1951. The avifauna of , its The Guam Rail is an endemic flightless origin, , and distribution. Univ. Kans. Publ. 3: l-359. bird, occurring in greatest abundance in the BALDWIN, P. H. 1947. The life history of the Laysan mixed woodland, second growth and scrub Rail. Condor 49:14-21. habitats of northern Guam, and uncommon- CARPENTER,R. E.,AND M. A. STAFFORD. 1970. The ly in savanna and mature forest habitats. It secretory rates and the chemical stimulus for se- is not found in . The rails are om- cretion of the nasal salt elands in the Rallidae. Condor 72:316-324. . ’ nivorous, preferring animal material, partic- KIBLER, L. F. 1950. Notes on the birds of Guam. Auk ularly gastropods and insects, over vegeta- 67:400-403. ble matter. The typical clutch consists of LINT, K. C. 1968. A rail of Guam. Zoonooz 41: 16-17. three or four eggs, with brood sizes ranging MAYR, E. 1945. Birds of the southwest Pacific. MacMillan Co., New York. from one to four (X = 2.0) chicks. Nesting OLSEN, S. L. 1973. A classification of the Rallidae. occurs year-round, but activity appears to Wilson Bull. 85:381416. increase during the rainy season (July-No- PEREZ. G. S. 1968. Notes on the breeding season of vember). The young are highly precocial, the Guam Rail, RaZZus owstoni. Micronesica achieving adult weights in the seventh 4: 133-135. RIPLEY. S. D. 1977. Rails of the world. David R. God- week of life and adult-like plumage after the ine, Boston. sixteenth week. Formerly distributed is- STONE, D. C. 1970. The flora of Guam. Micronesica land-wide, the Guam Rail recently has 6: 1-659. undergone severe range restrictions, vir- tually disappearing from southern Guam, and has become localized around the Division of Aquatic and Wildlife Resources, Depart- fringes of the northern plateau. ment of Agriculture, P.O. Box 23367, GMF Guam, Mariana Islands 96921. Accepted for publication 30 ACKNOWLEDGMENTS May 1979. This study was supported by Federal Aid to Wildlife Restoration (Pittman-Robertson Act). I thank the fol-

Condor, 81:408 0 The CooperOrnithological Society 1979

RECENT PUBLICATIONS

Research is a Passion With Me.-Margaret Morse Photographs, references (including a list of Nices’ pub- Nice. 1979. Consolidated Amethyst Communications lications), and index. Inc. 336 p. Paper cover. $9.95. Available: C. A. C. Inc., 60 Barbados Blvd., Unit 6, Scarborough, Ontario MlJ lK9. Canada. Margaret Morse Nice comDleted her au- tobiography aboutten years ago, a few years before she My World of Birds: Memoirs of an Ornithologist.- died in 1974. It has been edited here by Doris Huestis George J. Wallace. 1979. Dorrance & Co., Philadel- Speirs, president and founding member of the Mar- Dhia. 345 D. $10.00. Those who know of Dr. Wallace garet Nice Ornithological Club in Toronto, which as the author of an textbook may not be sponsored its publication. Woven into the principal aware that he previously did a classic life history study themes of Nices’ work on the birds of Oklahoma and of Bicknells’ Grav-cheeked Thrush and that he taught on Song Sparrows are her family history, experiences at Michigan State-University for many years. These &d with other ornithologists and participation in ornitho- other professional accomplishments were motivated by logical meetings. The story is fascinating and well-told. his sheer enjoyment of birds out-of-doors. He here re- Konrad Lorenz, a long-time friend, has written an ap- counts his career with characteristic ingenuousness preciative Foreword and an appendix in which he ex- and humor. An engaging autobiography, it will be en- plains his intellectual debt to her. This is a valuable joyed especially by those who know the man, himself. contribution to the history of American ornithology. Photographs, many from the family album.