Wilson Bull., 92(3), 1980, pp

Transcription

1 GENERAL NOTES Wilson Bull., 92(3), 1980, pp Growh and developmen of major body componens in he Monk Parakee.- The growh raes of a considerable number of bird species have been summarized (Ricklefs, Ibis 110:419-%51, 1968; Ibis 115: , 1973), ye among hese here are few records for hole-nesing species and none for parros. Caccamise and Alexandro (Wilson Bull. 88: , 1976) have since published informaion on he growh rae of Monk Parakees (Myiopsia monachus), bu hey considered only age-specific changes in body weigh. This paper provides informaion on egg size and nesling developmen and analyzes growh raes of major skeleal elemens of Monk Parakees. While mos species of parros are hole or caviy nesers, Monk Parakees are unique in building large enclosed sick ness, ofen communally (Caccamise and Weahers, Wilson Bull. 89: , 1977; Forshaw, Parros of he World, Doubleday and Co., New York, New York, 1973). These ness are occupied all year by maed pairs and by he young of he year for a considerable ime beyond fledging (Alexandro, M.S. hesis, Rugers Univ., New Bruns- wick, New Jersey, 1977). In a sric sense his species is no a rue hole-neser since he ness are consruced of sicks. Considering he ofen massive size (200 kg) and surdy consrucion of he ness (Roscoe e al., N. Y. Sae Fish and Game J., 1973), however, i is no surprising ha his species demonsraes he large cluch-size (5-9 eggs) and slow growh rae common in many hole-nesing species (Lack, Ibis 90:2545, 1946; Ricklefs 1968). M&o&.--Successive measuremens were made on 2 young in 1975 and 3 young in 1976, ha were reared in he oudoor fligh cage described by Weahers and Caccamise (Oecologia 18: , 1974). During boh years he pair producing he young were par of a group of 6 birds collecively housed. I supplied freshly cu privi (Ligusrum sp.) wigs for nesing maerial. These birds used o consruc he characerisic enclosed nes. The birds were provided wih waer, sunflower seeds, whie bread and dry dog food ad libium. Viamins were added o he waer, and fresh apples were placed occasionally in he cage. Though growh daa were colleced from neslings in only 2 ness, 9 ness were under observaion a various imes during his sudy. One of hese ness was buil by free-living birds in New Jersey (Caccamise and Alexandro 1976). The ohers were he resul of pairings by he re- maining birds in he cage. Daa were colleced on raes of egg-laying and egg morphology from all ness. In 1975, egg-laying was firs observed during he firs week in April when 2 eggs were discovered in he nes. This iniial aemp failed, when he female of he pair died. Afer anoher pairing, a second cluch was begun on 3 May. Of he 5 eggs in his cluch only 3 hached, 1 each day on 27, 28 and 29 May. In 1976, he firs nesing aemp began during he firs week in April when 3 eggs were laid. This aemp failed when he pair underook reconsrucion of heir nes on 13 April. The second cluch was begun on 5 May, wih 8 eggs laid by 15 May. The firs young hached on 30 May. The oher 3 eggs ha hached did so over he succeeding 3 days. One nesling (9 days old) died on 8 June. Measuremens of elemens represening maximum perpendicular disance beween aric- ular surfaces of bones were aken regularly on live specimens hroughou he growh period. They included bill widh (a base where bill emerges from skin); bill lengh (ip of upper rhamphoheca o disal edge of cere); bill deph (perpendicular disance from disal edge of cere o venral surface of lower mandible); and digi span (for his foo placed on fla surface and second and hird, oes aligned) which was recorded as he disance beween disal ends of erminal phalanges of oes 2 and 3. Body lengh was he disance from he op of he head 376

2 GENERAL NOTES 377 (wih bill held perpendicular o he long axis of he body) o he poserior end of he pygosyle. Also, feaher lengh was aken from he disal end o he poin of emergence from he skin. Measuremens also were aken from 9 caged aduls. Resuls.-Eggs from 3 ness were measured wihin 3 days of laying. For 28 eggs, he mean lengh (*SE) was 27.2? 0.20 mm (range mm) and he mean widh was 20.5 _ 0.15 mm (range mm). The mean weigh of 14 eggs was g (range g). Incubaion apparenly began wih he firs egg. During egg-laying females spend considerable ime in he nes, occasionally leaving for very shor feeding bous (Alexandro 1977). Haching is asynchronous, and a wide dispariy in nesling size is ypical. A haching, neslings had only a sparse covering of yellowish down, were incapable of locomoion and were blind wih eyelids fused. They did gape, bu seemed unable o raise heir heads. I firs heard a nesling vocalize on day 2. Tha comprised a shor 0.5 se see-eeep given repeaedly a 0.25 se inervals. By day 4 neslings showed limied coordinaed aciviy, only able o squa wih heir venral surface on he subsrae. They commonly rolled heir heads from side o side, using he bill as a pivo agains he subsrae, bu I never saw a head lifed a his age. Abou day 10 he eyelids began o open. Now neslings could unseadily hold up heir heads. By day 16 neslings held up heir heads wihou wavering bu, as heir legs remained fairly weak and of limied coordinaion, hey were capable of only limied locomoion. The recrices were conspicuously emerged by his ime bu naal down sill covered he remainder of he body. By day 18 he eyes were fully open, and primaries had begun o emerge. By day 20 neslings were able o sand seadily and firmly grasp a perch wih heir fee. They were quie acive and could use he bill for grasping. The major feaher racs of he body were well delineaed by day 24. The feahers of he head and wings were fully emerged, while many conour feahers of he body were sill in sheahs. On day 27 I firs heard a nesling emi an alarm call essenially similar o ha of he adul. A his age he neslings were very acive, flapping heir parially feahered wings and walking very quickly and srongly. A day 28 he body feahering was abou half developed, alhough much naal down remained (excep on he head). By day 37 mos conour feahering was complee, and lile down remained. The fligh feahers were sill emerging from sheahs, being less han 50% of adul size a his ime. The earlies fledging was observed on day 40. For each body componen growh was relaively uniform hroughou he firs 35 days of developmen, afer which growh slowed considerably (Figs. 1, 2). Linear regressions of age (hrough day 35) and percen adul size (Table 1) were highly significan (P < 0.01). While he growh rae was probably no uniform hroughou his period, as required for a ruly linear relaionship, he high r2 values indicaed ha he deviaions from lineariy were small. The slope of hese regression equaions provided an esimae of he overall growh rae during he iniial sages of developmen (Table 1). Wih he excepion of he arsomeaarsus, he skeleal elemens grew a very similar raes of 2-2.5% per day. The arsomeaarsus grew a raes significanly lower han all oher leg and wing elemens excep he ibioarsus, which was inermediae in value. The bill dimensions grew more slowly a a rae of abou 1.5% per day. Growh raes of he 10h primary and he innermos recrix were aken, beginning from he ime hey emerged from he skin (day 10 and 18, respecively); hus he growh raes of hese feahers did no correspond o he same period of developmen as he oher measuremens. Esimaes of relaive levels of mauraion a he end of he linear porion of he growh curve were indicaed by he raio of he mean nesling size a 35 days o he mean adul size (Table 1). In erms of linear dimensions, he wing was somewha more developed han he

3 378 THE WILSON BULLETIN * Vol. 92, No. 3, Sepember 1980 OrMANUS (mm) adul 20 [BILL LENGTH (mm) o RADIUS (mm) r 2o BILL DEPTH (mm) r 01 ID OL HUMERUS (mm) 5-BILL WIDTH (mm) 01 DAYS FROM HATCH FIG. 1. Size of body componens relaive o he number of days from he dae of haching. Open symbols represen he 1975 brood, and closed symbols he 1976 brood. The mean and range are indicaed for he adul measuremens. leg. For he leg and wing, boh he proximal and he mos disal segmens mos closely approached adul dimensions. The bill grew relaively slowly, and a 35 days i was sill well below adul size in boh lengh and deph, while widh was 92% of adul size. By day 35 primary 10 and he inner recrix were only 42% and 30% of adul size, respecively. Discussion.-Based on sudies of growh in 3 species of alricial passerines, O Connor (Ibis 119: , 1977) saed:... resources are allocaed a any ime o he growh of he componens wih he currenly highes funcional prioriy, hough wih due regard for fuure needs. Monk Parakees fledge a days. A he younger end of his range, which

4 GENERAL NOTES FEMUR (mm) 40.. l gp adul o- 0 p y SOr6ODY LENGTH (mm) 0 20 TARSOMETATARSUS r (mm) ~ PRIMARY a* l l... 9 P= a* 0 l a 0 x.. A B 0 4 i FOOT SPAN (mm)....a 40. l 0. na INNER RETRIX (mm l A 0.N.y A =:?I 01 4 a 1 DAYS FROM HATCH FIG. 2. Size of body componens, body weigh and feaher lenghs relaive o he number of days from he dae of haching. Open symbols represen he 1975 brood, and closed symbols he 1976 brood. The mean and range are indicaed for he adul measuremens.

5 380 THE WILSON BULLETIN * Vol. 92, No..?, Sepember 1980 TABLE 1 REGRESSIONS OF BODY COMPONENT SIZE (PERCENT OF MEAN ADULT SIZE) ON AGE; PERCENT OF MEAN ADULT SIZE AT 35 DAYS Bady camponen a b Sg % mean adul size a 35 days Humerus 15.4 Radius 12.8 Manus 12.2 Femur 28.2 Tarsomeaarsus 27.4 Tibioarsus 27.4 Toe span 13.2 Bill lengh 22.3 Bill widh 49.4 Bill deph 26.6 Tenh primary Inner recrix Body lengh a = Y-inercep from he regression equaion. 2 b = slope from regression equaion. 3Si = sandard error of he slope. * AU P = P s corresponds wih he age of maximum weigh, he body componens of greaes funcional prioriy, and hence greaes survival value would be expeced o be he mos nearly full grown. Comparisons of he percen mean adul size wih neslings a an age of 35 days provide an indicaion of he sae of mauraion, a leas in erms of size, a abou he ime of fledging. Since his species is an arboreal neser, fledging age is probably a funcion of he aainmen of fligh capabiliies. By day 35 boh lenghs of body and wing componens were eiher of adul size, or nearly so. By comparison, major leg bones had no aained adul lengh even hough hese elemens a haching were considerably more advanced han he wing bones. This is evidenced by he much higher Y-inerceps for regressions of leg bone lengh on age (Table 1). O Connor (1977) suggesed ha early developmen of he leg, paricularly he arsomeaarsus, is imporan in some alricial species because he neslings mus have he abiliy o orien and exend hemselves owards he adul during begging and feeding. In conras o he Monk Parakee, in which leg growh and coordinaion is lae, alricial species discussed by O Connor (1977) hach synchronously and are fed by he parens in response o begging behavior. Though feeding of Monk Parakee neslings in he nes has no been observed, i seems unlikely ha begging is of primary imporance in his species, a leas early in developmen, since he young appeared unable o raise heir heads unil afer day 8. In addiion, asynchronous haching of eggs in Monk Parakees resuls in a wide dispariy in age among he neslings. Assuming ha 1 egg haches per day, wih a g-egg cluch here would be a considerable dispariy in age and size beween he oldes and younges nesling. If begging alone elicied feeding behavior by he parens, he younges nesling would be a a severe disadvanage under all circumsances, excep when all he older siblings were saiaed.

6 GENERAL NOTES 381 By day 35 foo span already averaged 99% of adul size. Rapid aainmen of adul foo size likely reflecs he imporance of he many asks he foo performs (e.g., perching, climb- ing, feeding). A haching, bill widh was already 49.4% of adul size, alhough, a day 35, bill widh was closer o adul size han lengh or deph. This was he resul of a more rapid developmen in widh before haching, since he growh raes of all bill dimensions were abou he same hroughou nesling developmen. Since bill widh was measured a he base of he bill, i is abou equivalen o gape widh. The rapid increase of gape widh in oher species (Dunn, Condor 77: , 1975; Holcomb, Nebraska Bird Rev. 36:2232, 1968; Holcomb and Twies, Ohio J. Sci. 68: , 1968; Royama, Ibis 108:313347, 1966) has been inerpreed (O Connor, Ibis 119: , 1975) as imporan in increasing parenal feeding efficiency because i allows he young o consume larger food iems. Young Monk Parakees are fed by regurgiaion. This maerial was described as a whie, milky fluid (Alexandra 1977). Ac- cordingly, he abiliy o consume large food iems may be of lile value o neslings. Since food is provided by he parens in a raher processed form, here would be lile advanage in rapid bill growh for he purpose of processing food iems. Fledglings, oo, are fed by regurgiaion, alhough hey soon begin o do some foraging for hemselves. Ye, as Pormann (Proc. 11h In. Omihol. Congr , 1955) has shown, as he brain develops early, he skull mus develop similarly o accommodae i. Thus, he greaer mauriy in bill widh may simply reflec he need for early skull developmen. Acknowledgmenrs.-For heir conribuions hroughou he course of his sudy I wish o hank Thelma Arculin, Peer J. Alexandra, Susan Ford and Charles Wagg. This is a paper of he Journal Series, New Jersey Agriculural Experimen Saion, Cook College, Rugers, The Sae Universiy of New Jersey, New Brunswick, New Jersey.-DONALD F. CACCAMISE, Dep. Enomology and Economic Zoology, Rugers, The Sae Univ. New Jersey, New Brunswick, New Jersey Acceped 1 June Wilson Bull., 92(3), 1980, pp The influence of agriculure on avian communiies near Villavicencio, Colom- hia.-desrucion of naural vegeaion o mee demands for increased agriculural produc- ion has resriced he disribuion of cerain avian species in Colombia, while benefiing ohers (Olivares, Smihson. Conrib. Zool. No. 26:77-87, 1970; Munves, Auk 92:307321, 1975). In regions where a sysemaic conversion o agriculure is occurring, sudies of he avifauna adaped o he alered habias would have predicive value. Blydensein (Ecology 48:1-15, 1967) described a recen wesward exension of he savanna as foress were cleared a he wesern edge of he Llanos Orienales, implying changes in avian communiy com- posiion. This paper examines habia usage by bird species on a represenaive agriculural area in his region and asks: how do presen land-use rends affec species abundance disribuion? Sudy area.-the wesern secions of he Deparmen of Mea and he Inendencia of Casanare were formerly covered by a Piedmon rain fores which exended easward from he Andean foohills, gradually merging wih he savanna and gallery foress ypical of he Colombian Llanos (Baes, Geogr. Rev. 38: , 1948). During he las 3 decades, foress have been diminished grealy in he viciniy of Villavicencio, Mea, and he land convered o he producion of rice and cale. Fieldwork was conduced a he Hacienda La Corocora (3 57 N, W; elev. 310 m) 35 km SE of Villavicencio. Deailed descripions of vegeaion and climae in his region are given by Baes (1948) and Blydensein (1967). Annual precip- and