(1947) made a similar study of the English Blackbird (Turdus m.

Size: px

Start display at page:

Download "(1947) made a similar study of the English Blackbird (Turdus m."

Cornelius Poole
5 years ago
Views:

1 MARKED DISPERSAL AND FLOCKING OF YOUNG ROBINS (TURDUS M. MIGRATORIUS) AFTER FLEDGING By DAVID H. HIRTH, ALBERT E. HESTER, and FREDERICK GREEI. EY a INTRODUCTION The phenmenn f Ortstreu (rientatin t the place f birth) has been well dcumented in many birds, including the American Rbin (Turdus m. migratrius). We have presumed that early learning abut the envirnment is the mechanism by which the instinctive capabilities f Rbins and ther birds are directed. With this in mind we have examined the mvements f Rbins during the pst-fiedging perid. Amng the birds in which Ortstreu has been studied is the Pied Flycatcher (Muscicapa h. hypleuca). Curi (1958) fund that 10 percent f 710 Pied Flycatchers banded as nestlings returned t the same 1,800 acre study area the fllwing year, and that nethird f this number returned within 2.5 miles. In Kluijver's (1951) study f the Great Tit (Parus m. majr), the majrity f the firstyear birds nested within 800 meters f their birthplaces. Werth (1947) made a similar study f the English Blackbird (Turdus m. merula) and Sng-thrush (T. e. ericetrum), bth clsely related t the American Rbin. In the case f the Blackbird 93 percent f 157 birds recvered as breeders, which had been banded as nestlings, were fund nesting within five miles f their birthplaces. The Sng-thrush was nly slightly less hme-riented, and 83 percent f 126 similarly banded first-year adults were nesting within five miles f their birthplaces. A study f the hming tendencies f the American Rbin was made by Farner (1945). He stated that "there is a marked tendency amng Rbins t return, as breeding birds, t their birthplace r its immediate vicinity." Frm a sample f 428 Rbins banded as nestlings and recvered as adults, he fund that 92 percent returned t breed the fllwing seasns within 25 miles f the place where they had been banded. In an earlier study, Hickey (1943) used recrds f 61 Rbins that had been banded as nestlings and recvered in subsequent years by nn-banders, thus assuring a representative sample. Fifty-fur percent f these birds were fund within ne mile f the place f banding, and an additinal 20 percent were fund frm ne t ten miles away. Despite the number f studies which have been made f the return f adults t their birthplaces, we knw f very little infrmatin Department f Wildlife and Fisheries, University f Michigan, Ann Arbr, Michigan W07 West 12th St., Jacksnville, Arkansas adept. f Frestry and Wildlife Management, Univ. f Mass., Amherst, Mass

2 Vl. 40, N. 3 Dispersal and Flcking f Marked Rbins [209 Figure 1. Map f Amherst, Mass. shwing bservatins f fledgling Rbins and lcatin f nests frm which they fledged. N DISPERSAL OF NESTLING ROBINS 1963-'64'65 45 I[ 01VIDUALS B ß ß FLEDGLINGS SEEN ONE OR MORE TIMES NESTS FROM WHICH FLEDGLINGS WERE SEEN AT A O NESTS FROM WHICH FLEDGLINGS WERE SEEN AT B, C, D. e NESTS FROM WHICH FLEDGLINGS WERE SEEN AT BOTH A AND B, C0O. O NESTS FROM WHICH FLEDGLINGS WERE SEEN ELSEWHERE (NOT& r B,C )) ß ß E O ß ß A STATE TREE NURSERY B RASPBERRY PATCH C BLUEBERRY PATCH D CHERRY ORCHARD E ROOST F ROOST SCALE OF n the dispersal f yung birds in the interval frm fiedging t fall migratin. Experience gained in this perid prbably is respnsible fr establishing the behaviral patterns evidenced in Ortstreu. Kluijver (p. cit.) nted that the distance that fledgling Great Tits were led frm the nest by their parents was apprximately equal t the distance frm the birthplace that the majrity f first-year Great Tits established their wn nests. Recveries f banded yung fr 12 weeks after leaving the nest were reprted by Werth (p. cit.). She fund fr the Blackbird and Sng-thrush that 70

3 210] D. H. Hi th, A ß E. Hester., and F. G 'eele t. Bird-Banding July 1969 and 55 percent respectively f recvered birds were still in the vicinity f the nest after 12 weeks and that an additinal 15 and 18 percent respectively were within five miles f their birthplaces. Althugh these species are clsely related t the Rbin they d nt necessarily represent analagus situatins, because bth are nly partially migratry. Our study is the result f three years f bservatins f the mvements f tagged Rbins frm the nest until fall migratin. The study was supprted by the Agricultural Experimentatin Statin, University f Massachusetts at Amherst, }¾[assachusctts with Hatch and Cperative Reginal Research funds. The data were gathered by the first tw authrs in the curse f graduate study. MATERIALS AND METHODS We cnducted this study in the "twn" f Amherst, Massachusetts (Fig. 1), an area encmpassing a small business district, schl and cllege campuses, residential districts, agricultural land and wdland. The area was abut 25 square miles, althugh ur study was cncentrated n abut ne-third f this area. One hundred and eighty-three nestling Rbins were marked during the summers f 1963, 1964, and This was dne with U.S. Fish and Wildlife Service leg-bands and with plasticizd clth wing-tags (Hcstcr, 1963). The tags were rughly circular with a diameter f ne and ne-half inches and were attached t the bird by an aluminum pultry clip inserted thrugh the patagium. All tags were "rcket-red" and had cmbinatins f letters r numbers painted n them fr individual field identificatin. As far as we culd determine there was n impairment f physical abilities r behavir f tagged birds. Hcstcr (1964) reprted that he wing-tagged 125 nestlings in 51 successful nests frm which 130 birds fledged (2.56/nest). Hirth (1966) fund 14 f 117 tagged nestlings did nt survive t fledge and that the fate f 35 thers was unknwn. These data are similar t thse reprted by Hwell (1042). Observatins f tagged birds were made with a sptting scpe equipped with a twenty-pwer, wide-angle eye-piece and munted n a rifle stck fr ease f handling. Individual birds culd be identified at ranges up t 100 yards. One r bth tags usually lasted as lng as the birds were under bservatin, althugh we knw sme tags were lst between fall migratin and return the fllwing spring. Thirty-nine birds tagged as nestlings were knwn t have died n the study area. Unfrtunately, it was nt pssible t estimate accurately the age f the bird when it died ften enugh t prvide a mrtality rate fr these birds during the first few mnths pst ficdging.

4 , l. 40, N. 2, Di 'persa! and Flcking j' Marked Rbzns [211 Figure 2. Mvement f fledgling Rbins in relatin t weeks pst-fiedging and distance frm nest. Distances (in miles) in Part B are shwn at the base f each bar. A. NUMBER OF INDIVIDUALS OBSERVED IN RELATION 60 TO DISTANCE n, 50 u 40 Weeks after fledging <[ 5 z 20 i 5 8.I DISTANCE FROM NEST (MILES). c I00 B. PERCENT OF FLEDGLINGS OBSERVED IN RELATION TO AGE n, c= z. $0. 20 z n 0.I ) 4'.I I 2 : WEEKS AFTER FLEDGING

212] D. H. Hirth,.4. E. Heste, and F. Greeley Bird-Banding July, 1969 RESULTS One hundred and six f 183 nestlings tagged ver three years in this study were bserved after fledging.

5 212] D. H. Hirth,.4. E. Heste, and F. Greeley Bird-Banding July, 1969 RESULTS One hundred and six f 183 nestlings tagged ver three years in this study were bserved after fledging. The dispersal f these birds was pltted graphically fr an eight-week perid (Fig. 2). These shw the expected gradual mvements f these birds away frm the nest in this time. At the end f three weeks the largest number f birds was still t be fund near their parents' territries, r within 0.1 mile f the nest. Between fur and six weeks after fledging mst f the birds had mved nly 0.2 miles frm the nest. After eight weeks 27 percent f the 30 birds still under bservatin remained abut 0.2 miles frm the nest and 33 percent had mved 0.5 miles r further. The length f time that individual fledgings remained within r clse t their parents' territries was quite variable. In spite f the cnspicuusness f the tags, sme individuals were difficult t bserve at frequent intervals, but it was pssible t bserve dispersal amng fledgings seen reasnably ften. Ten yung birds frm nests within a ne-furth acre area n the University f Massachusetts campus, presumably influenced by similar envirnmental cnditins, remained fr an average f lzi.5 days near the nest site in The length f time varied frm five t 32 days. One individual disappeared after five days and was seen again a mnth later 0.zi miles frm the nest. Cnsiderable variatin was bserved even amng nestmates. In ne instance, tw members f ne brd left the territry after 13 days, while a third remained there fr 32 days. In anther case, three nestmates remained eight, 11, and 22 days in the vicinity f the nest. Werth (p. cit.) presented data in tabular frm n the dispersal f yung Blackbirds and Sng-thrushes frm their natal areas. A cmparisn f her data with ur wn indicated that the rate f dispersal frm the vicinity f the nest was abut equal in all three species. Small differences which d exist may reflect differences in sampling techniques r in availability f fd. Kale and Jennings (1966) clr-marked a grup f immature Mckingbirds (Mi nus plyglttus) feeding in a swamp near St. Petersburg, Flrida and fllwed their mvements after the surce f fd, which had initially attracted them, was used up. The majrity f these birds mved less than five miles and the furthest sighting was 11 miles away. We d nt knw hw all yung Rbins find their way t feeding areas. Cncentratins f feeding and rsting Rbins during the summer have been recrded by many bservers. These flcks are ften cmpsed f many yung and lesser numbers f adults. In a study n ur campus, Smith (1963) fund 63 percent f 2zi7 Rbins captured in a cherry rchard early in the summer were yung individuals. Over 90 percent f a like number f Rbins, captured in a nearby highbush blueberry planting later in the summer, were yung. Adults were bserved feeding n dmestic cherries, and sme were knwn t carry cherries as far as ne-half mile t their nestlings. The grund beneath such nests was ften littered with cherry pits. Rbins may carry ther fruits t their

6 Vl. 4, N. : Dk persal and Flcki g f Marked Rb 'n. [213 nestlings, but mst ther fruits d nt ripen until after the nesting seasn. Furthermre, we twice bserved fledglings near their nests being fed by adults ther than their marked parent. It is apparent, therefre, that sme yung may becme riented t surces f fd, such as fruit, by fllwing their parent r ther adults. One marked fledgling, fr example, was bserved leaving its nest-area with its parents. They flew tward a cherry rchard ne quarter f a mile frm the nest, and the marked nestling was seen there tw days later. A nestmate f this individual als appeared at the cherry rchard, but was nt seen with adults after leaving the nesting area. In the vicinity f the University f ([assachusetts there were tw general areas where Rbins cncentrated in the summer. One area (sites B, C, and D in Fig. 1) was assciated with the University rchards where there were cultivated cherries and blueberries, and wild black raspberries (Rubus ccidentalis). The ther area (site A in Fig. 1) was lcated at a state tree nursery and a University farming area. It prvided cultivated blueberries, wild tatarian hneysuckle (Lnicera tatarica), and black cherries (Prunus sertina). There was a steady fruit supply at this area fr a full six weeks each summer. The large number f tagged fledglings utilizing the surce f fd at site A was nt surprising in view f the fact that 33 percent f the 52 nests which prduced flying yung were lcated just 0.2 miles away at the state tree nursery. The stability f this feeding flck was reflected by the almst equal numbers f tagged fledglings at the 0.2 mile range in the perid frm three t eight weeks after fiedging (Fig. 2A). The prximity f this excellent nesting area t these fruit crps apparently diminished the rate f dispersal and gave rise t the bimdal distributin f ranges fr yung at eight-weeks pst-fiedging (Fig. 2B). These tw general feeding areas were abut 0.7 miles apart. Over a three year perid nly fur tagged fledglings, f 56 which fed at these sites, were knwn t have utilized bth feeding areas. There was a marked tendency fr iramatures frm nests within apprximately ne-half mile f site A t gravitate tward this surce f fd. Mvement f fledglings frm nests surrunding sites B, C, and D tward these surces f fruit was nt at all prnunced. This was prbably because there was nt as large a quantity r as cntinuus a supply f fd as there was at site A. Each f the feeding areas where flcks ccurred had an area adjacent t it which was suitable fr lafing during the heat f the day. Lafing sites were in pen stands f cniferus r deciduus trees with a clsed canpy and very little undergrwth. Rbins spending the day in these areas als fed upn invertebrates in the frest litter. Site tenacity f Rbins t these lafing areas was quite weak cmpared t the persistence with which they cntinued t use surces f cultivated and wild fruit. The pattern set by adult birds is prbably very imprtant in the establishment f feeding and scial assciatins f the iramatures. In 1963 Hester (this study) bserved small flcks f apparently nn-breeding adults f bth sexes which became 'gathering pints"

7 ... ß lulv, 1.0(;9 fr pst-breeding adults and immatures. Such flcks were nt, bserved in ther years f this study. As members f feeding flcks. tagged immatures under bservatin maintained the same range as did adults. These flcks remained intact as lng as the surce f fruit was available, and there was little interchange f individuals between feeding flcks. After the fruit crp was gne at a given lcatin, sme tagged yung remained in the same area, thers disappeared entirely, and a few were seen a mile r mre frm the initial feeding site. Seven nestlings, ut f 106 knwn t have reached the flying stage in this study, were bserved mre than a mile frm the nest in the curse f the summer. One f these traveled 5.6 miles, but the thers mved less than 2.5 miles. Additinal tagged yung undubtedly mved farther than ne mile, but we were unable t fllw such scattered mvements. Limited bservatins f rsting habits f recently fledged yung indicated that these birds became regular members f rsting flcks as sn as they jined feeding flcks. The first tagged immatures were seen entering a rst in 1965 n June 11, the same day that yung were first nted with a feeding flck. This partieular rst was nly 100 yards frm the feeding area at A (Fig. 1) used by mst f this rsting flck. It seems likely that it tk lnger fr fledglings t arrive at rsts mre distant frm feeding areas. Frm June 11 n, rsting flcks grew steadily in size as increasing numbers f immatures jined them and increasing numbers f adults cmpleted their nesting cycle. As with feeding flcks, we bserved very little interchange amng members f rsting grups. Only tw ut f 22 tagged yung identified at rsts were seen at mre than ne rst. On a brader scale, nly six percent f 93 tagged immatures and adults seen at rsts had appeared at mre than ne rst. It appeared t us that small rsts tended t be abandned late in the summer, while large rsts persisted as late as the end f Octber. Undubtedly, rsting and ther flck activities are prgressively influenced by migrants after September 1. Because summer feeding flcks dispersed t a large extent during the mnth f August, little infrmatin cncerning the fall migratin was btained frm tagged Rbins. Nine tagged immatures were identified in Amherst during Octber, the last ne being seen n the 29th. The average distance f these birds frm the nest was 0.8 miles--tw were still within 0.1 mile and ne had mved 2.3 miles. The last migrants left Amherst during the last three days f Octber in Five adults and fur immatures were last seen in Nvember (1963). Seven tagged Rbins (5 adults and 2 f unknwn age) wintered in Amherst during this study. SUMMARY AND CONCLUSIONS One hundred and eighty-three nestling Rbins were wing-tagged fr individual field identificatin during the summers f 1963, 1964, and One hundred and six, r 58 percent, f these birds were bserved after fledging; f the remaining 42 percent mst were nt bserved a ain. These birds typically remained in the vieinit. v, f

8 v l.. ',. : 1) ;, per, al and Flcking their parents' territry fr abut three weeks. Fledglings made their way frm the nest area t nearby surces f abundant fruit where many jined feeding flcks f adults and ther immatures. Fledglings smetimes fllwed parents r ther adults t feeding areas. In this study yung usually traveled less than ne half mile t an initial feeding lcatin. A lafing site was assciated with each feeding area. Members f feeding flcks ranged abut ne quarter mile frm a central surce f fd. Flcks remained intact until the fruit supply was exhausted. Immatures jined rsting grups at the same time as they jined feeding flcks. There was little interchange amng members f feeding flcks r members f rsting flcks. Interspersin f cver within the cruising radius f yung Rbins was prbably an imprtant factr influencing their dispersal. It seemed t us that the interspersin within ne half mile f the nest was favrable and may have limited the rate f gegraphical spread f yung frm their nest. We d nt knw whether this limitatin n their pre-migratry experience influenced the distributin f nest sites chsen by the yearlings in the fllwing spring. The mvements f yung Rbins which we bserved, hwever, seem t cnfrm with Hickey's (p. cit.) bservatins f the distances at which yearling Rbins nested frm the sites at which they had fledged in the previus year. LITERATURE CITED Cum, E Geburtsrtstreue und Lebenswartung junger Trauersehn/ipper (Muscicapa h. hypleuca Pallas). Vgelwelt 79: FARNER, D. S The return f Rbins t their birthplaces. Bird-Banding 16: HESTER, A. E A plastic wing tag fr individual identificatin f passerine birds. Bird-Banding 34: H STEa, A.E Eclgical relatinship f the Eastern Rbin t cmmercial fruit crps in Massachusetts. M. S. Thesis, Vniv. f Mass., Amherst. 94 pp. H CKEY, J.J A Guide t Bird Watching. Oxfrd University Press, New Yrk. 262 pp. H TH, D.H An eclgical study f the rbin in Amherst, Massachusetts. M. S. Thesis, Univ. f Mass., Amherst. 77 pp. HwEnn, J. C Ntes n the nesting habits f the American rbin (Turdvs migratrius L.). Am. Midland Naturalist 28: K xn, H. W. II, and W. L. JENN N6S Mvements f immature Mckingbirds between swamp and residential areas f Pinellas Cunty, Flrida. Bird-Banding 37: Knu vea, H. N The ppulatin eclgy f the Great Tit, Pay'us m. majr L. Ardea 39: SU Tn, H. N A study f envirnmental and ppulatin factrs in relatin t damage t rchards caused by birds. M.S. Thesis, University f Massachusetts, Amherst, Mass. 138 pp. WEaTH, I ENE The tendency f Blackbird and Sngthrush t breed in their birthplaces. British Birds 40: Received June, 196.

Official Swine Ear Tags

Official Swine Ear Tags Swine Identificatin 101: Understanding Swine Ear Tag Requirements Due t a cntinued emphasis n livestck traceability within state and federal agencies and the livestck industry,