DEMOGRAPHY OF THE COOPERATIVELY BREEDING GALAPAGOS MOCKINGBIRD, NESOMIMUS-PARVULUS, IN A CLIMATICALLY VARIABLE ENVIRONMENT
DEMOGRAPHY OF THE COOPERATIVELY BREEDING GALAPAGOS MOCKINGBIRD, NESOMIMUS-PARVULUS, IN A CLIMATICALLY VARIABLE ENVIRONMENT
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DOI：
10.2307/4841
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发表时间：
1989-06-01
影响因子：
4.8
通讯作者：
GRANT, PR
中科院分区：
文献类型：
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作者：
CURRY, RL;GRANT, PR
(1)加拉帕戈斯知更鸟是一群地域性的合作繁殖物种。用11年(1978-88)的时间研究了热那维萨岛的种群特征，包括7年中雨年、2年厄尔尼诺-南方涛动(ENSO)极端潮湿年和2年干旱年。(2)成虫的年存活率(x=61%)在平均条件下较高，但在干旱年份和流行病期间都很低。雄性的存活情况略好于雌性。成人的存活率不随年龄变化，但青少年的存活率较低(x=35%)，变数是成年存活率的两倍。(3)嘲鸟根据降雨进行繁殖，每个繁殖的雌鸟每个季节最多产5.2只雏鸟(x=2.3)。在多雨的年份，幼鸟的窝卵数、窝卵数和总产量都有所增加。助手照顾了35%的鸟巢，使雏鸟的产量增加了19%。(4)不同的死亡率导致了成人性比的差异。雄性的繁殖受到雌性相对稀缺的限制，雄性充当助手的比例也相应地有所不同，因为非繁殖的雄性最常起到帮助作用。雌性繁殖的比例不随成虫性别比而变化，因为一夫多妻制是在雌性占主导地位的2年内发生的，少数雌性也参与了繁殖。(5)出生率和存活率的差异导致种群密度的显著变化，但繁殖者的密度(C.V.=21%)与非繁殖者的密度(C.V.=93%)保持相对恒定。在几乎整个研究过程中，这些常年守卫的群体领地占据了所有可用的栖息地。(6)种群规模平均为4.2只成虫，每群最多4只繁殖雌鸟。在种群密度高和一岁幼崽占主导地位的年份，种群规模更大，多种群更频繁；67%的一岁幼崽留在它们的出生地，47%的雌性和62%的雄性也是第一次繁殖。(7)气候变化对知更鸟社会组织的影响主要是通过其对出生率和存活率的影响，间接影响种群的S密度、年龄结构和性别组成，由于气候引起的种群变化有利于幼鸟在没有建立独立领地的情况下进行繁殖，因此该物种保持了多元繁殖。
(1) The Galapagos mockingbird is a group territorial and cooperatively breeding species. We studied its demography on Isla Genovesa for 11 years (1978-88), a period that included 7 years with moderate rainfall, 2 extremely wet years when El Nino-Southern Oscillation (ENSO) event occurred, and 2 drought years. (2) Annual survival of adults (.hivin.x = 61%) was high during average conditions but lowere in both drought years and during an epizootic. Males survived slightly betternthan females. Survival did not vary with age among adults, but survival of juveniles was lower (.hivin.x = 35%) and twice as variable as adult survival. (3) Mockingbirds bred in response to rainfall, producing up to 5.2 fledglings per bredding female each season (.hivin.X = 2.3). Clutch size, number of clutches and total production of fledglings increased in wet years. Helpers attended 35% of all nests and increased production of fledglings by 19%. (4) Differential mortality produced variation in the adult sex ratio. Breeding by males was constrained by the relative scarcity of females, and the proportion of males acting as helpers varied correspondingly because non-breeding males most often helped. The proportion of females breeding did not vary with adult sex ratio, because polygyny occurred in 2 years when females predominated, and most of the few females the helped also bred. (5) Variation in natality and survival caused substantial variation in population density, but the density of breeders remained relatively constant (C.V. = 21%) compared to density on non-breeders (C.V.=93%). Group territories, which were defended year-round, filled all available habitat througout virtually the entire study. (6) Group size averaged 4.2 adults, with up to four breeding females in each group. Groups were larger and plural groups more frequent in years when density was high and when yearlings predominated in the population; 67% of yearlings remained in their natal territories, where 47% of females and 62% of males also first bred. (7) Climatic variation influences mockingbird social organization mainly through its effects on natality and survivorship, which indirectly influence the population''s density, age structure, and sex composition. Plural breeding is maintained in this species because climatically-induced demographic variation favours the tendency of young birds to breed without establishing independent territories.