BIRD LONGEVITY in the EASTERN HIGHLANDS of ZIMBABWE - FIRST REPORT D B Hanmer
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BIRD LONGEVITY IN THE EASTERN HIGHLANDS OF ZIMBABWE - FIRST REPORT D B Hanmer Mitsasa, ]'O Box 3076, Paulington, Mutare, ZIMBABIIT Introduction Hanng agreed to concentrate on sunbirds, La Rochelle Botanical Garden. Penhalonsa A complete change of scene; frorn the torrid (18"54'S, 32'42'E) was an obvious choici. swamps of Malawi's lower Shire valley to It is north of Mutare, south of Penhalonga, the mountains on Zimbabrve's eastem bordeq with an altitude similar to that at Mitsasa. where there is a somewhat different avifauna, The rainfall is greater, although the streams although many 'old friends' are present. After and dam dried up in the droueht. The sur- four years of nnging a wrde variety of birds rounding natural vegetation has Seen replaced in the Mutare area, it seems time lo assess almost entirely by pine and Eucalvntus the results obtained so far, particularly as the pfantations. bui soh6 miombo md iiacia penod included a malor drought. remain nearby. Howeveq nets are only set among exotii flowenng shrubs. in miinly Sites exotic forest and in the aloe garden. Trapping has taken place monthly from July 1990 to Mistnetting started at Mitsasa, Fern Valley May 1.994 (unfortunately June 1994 was (19'03'S, 32"39'E, altitude I 200 m) in mrsseo). July 1990, on a very erratic basis, but us- ually on two to four days a week, and The Vumba Botanical Garden, on top of the continued thus to the end ofJune I 994 The Bvumba Mountains ( I 9'07'S, 32"47'8, site ts on a hillside south of Mutare, in the altitude I 550 m) is also a good place for sun- rain shadow of the Bvumba Mountains and birds and the surrounding montane forest and the vegetation is mainly dry, open miombo grassland are home to other groups which woodland with some Acacia,,Termrnalia come into the garden shrubbenes where the (which is the main vegetation type in the nets are set. The rainfall is hieh and the dam valley bottom). As yet, exotic flowering held water during the drought. Trapping shrubs and planted aloes are too small to started in August 1990 and has continued have altered the basic habitat much, but monthly up to May 1994 there is more sunbird food than is normal in miombo woodland As there are bird Mountain Home, Penhalonga (18"50'S, baths and a feed table with 'wild bird' seed, 32'41'E, altitude I 460 m) is a private home other groups also find more sustenance than on the side of a border mountain north of is usual in the area. Penhalonga, with a high rainfall. Hundreds of sunbirds flock there to feed on Droteas. Miombo woodland does not support a large aloes and exotic plants in the garden, but avifauna, although a good variety occufs, montane forest and grassland species also so it seemed that Mitsasa could never occur. Trapping only started there, mainly compare with Nchalo, Malawi, as a ringing among the proteas and near the ever-full bird station; other sites were needed, where bath, in July 1992 when rhe droughr was more than 1,8 birds might be caught per approaching its height and has continued trapping day. monthly to May 1994. Safring News 23 55 I 991 Table l. Number of indivrduals nnged and recaptured or resiehted in the Mutare area befween July 1990 and June 1994. showing probable effect of &ought in l99l-1992 and poor rains rn I 992- I 993 Year Number Number and percentage recaught after nnged nnged <l vr >l yr (%) >2 yr (.%o) >3 yr (%) I 990- I I 049 149 93 (8,e) 28 (2.7) I I (2,0) 1991-2 I 364 217 48 (3,5 ) 20 (1.5) 1992-3 I 171 u4 48 (4,1) l 993-4 I 019 7'7 Totals 4 603 557 189 ,18 2l Hillcrest College, Penhalonga ( I 8'55'S, two-vear level there is a reduction in the 32"39'E) is quite close to l.a Rochelle, al- percentage retrapped in I 993-l 994'fromthat though lower and much dner but so tar has retrapped in 1992-1993, but that figure is only been used for rurging demonstrations, probably also low. when the presence of a lot of children has precluded the capture of many birds. The Table 2 gives a breakdown of the numbers vegetation is basically dr 1- ,lcacra scrub and ringed and retrapped or resighted at the both Whitebellied and Scarletchested different sites, with the percentage which are Sunbnds ltlectarrnra talatala and lr{. ,senesal- known to have lived for at least one year. *r.sls occur there, while at the other sites thev Hillcrest College may be ignored, but of the do not. so perhaps more work slrorrld be done others. there. Mitsasa has the lowest retrap rate, possibly Results because it was most affected by the drought. Even so, 6.0%o were present in the garden Table I shows the number of birds nnsed at one or more yezus after being ringed, con- all five sites between Julv l9()0 and sisting mainly of seedeaters and omni-vores June 1994 and the number of indir.rduals other than sunbirds, although one Miombo recaptured or resighted at least once dunng Sunbirdl has been recaptured after more than that time (manv birds have been colour- three years. ringed). Many birds have been seen or caught several times and the present annual retrap La Rochelle shows a different prcture, with rate is over 25% of the number nnged, which good numbers recaptured even at the thtrd bodes well for the lons-term studv of year level, more than fwo thirds of these were indruduals of a vanety of species. However. sunbirds. Vumba B.G. shows a low recapture looking at the "number and percentage re- rate at both the first and second year level, trapped after more than one year" column, it but the high number recaptured in the third is evident that something, presumablv the year (mainly sunbirds) bnngs up the overall l99l-1992 drought, reduced the percentage percentage. Mountain Home, where trapputg of birds which were recaucht after one vear rLatin dunng I 992-1993 and t gq:- t 994 Ai the names are siven in Table 4. Safring I'lews 23 56 1994 Table 2. Number of individuals nnged and recaptured or resighted at five sites in the Mutare area between July 1990 and June i994. including one bird ringed elsewhere, but refrapped at Vumba Botanical Garden during 1990-1994. Also shown, number ringed to June 1993 and total number and percentage knor.m to have lived for more than one year after being nnged. Mit : Mitsasa, La R : La Rochelle, VBG : Vumba Botanical Garden. Mt H : Mountarn Home, H C: Hillcrest College. Site Number nnged Number recaught after Number nnged Totai sumnng to June 94 <lyr tlyr >2yr >3yr to June 93 >lyr (%) Mit I ll2 220 38141 887 ]J (6,0) LaR I /)O 210 84 25 t2 | 526 t2l (7,e) VBG t 0l4 75 37 9 8+l /)) 54 (7,2) MtH 706 52 30 40t 30 (7,5) HC t5 0 0 0 Totals 4 603 )) / 189 48 2l+ I 3 569 2s8 (.7,2) only started in the middle of ttre drought, despite the drought. That a large bird like the shows a fairly high first year recaprure figure, thrush should have survived for over three two thirds of which consists of sunbirds. years (at Vumba B.G.) is not surprising, but the recapture of an apalis there after three Table 3 shows the number of birds ringed years is more unexpected. That three annually at four sites up to Jture I 993, in order seedeaters (one fiom Vumba B.G. and nro that nnged birds u'ould have had a chance to from La Rochelle) have been recaught after be refrapped up to twelve months later, and over three years is most surprising, con- the number and percentage known to have sidenng the lack offood after the drought. lived for more than one. two or three vears. Here the 'drought effect' is more obvious, Table 5 lists the known minimum aee of the with considerable reduction in the number of 45 oldest recaprured or resighted biids. ege birds recaptured in 1992-1993 and 1993- was calculated with reference to the dates of 1994 at some sites, but the results are very first and last capture, to the breeding season vaned. At Mitsasa in 1993-1994, ouite a lot and to the appea.rance of the bird. of birds were recaught after one or two years. whereas at La Rochelle and Vunrba B.G. in Where signs of immaturitywere observed on 1993-1994, a fatrly large number were re- the first occasion, a bird was aged to the caught only at the three-year level. nearest six months, but where it was ap- parently adult when nnged, an estimate was Table 4 shows how many individuals of made of the minimum time required for that which species are known to hal'e lived for species to lose all signs of immarunry and more than one, two or three years. It includes this was added to the trme elapsed between a wrde vanefy, but a surpnsing number of nngrng and last capture or sigirtrng, the age srurbirds have been recaught over a falrly long being grven as "more than" the total, also to penod of time (especially at La Rochelle), the nearest six months. Safring News 23 fi I 991 Table 3.