The Red Canary Tim Birkhead The creation of Dolly the sheep in the s was for many people the start of a new era: the age of genetically modified animals.
However, the idea was not new for in the s an amateur scientist, H The Most Perfect Thing Tim Birkhead 'I think that, if required on pain of death to name instantly the most perfect thing in the universe, I should risk my fate on a bird's egg' Thomas Wentworth Higginson, How are eggs of different s De zintuigen van vogels Tim Birkhead. Het vogelei Tim Birkhead Waarom hebben eieren de vorm die ze hebben? Waarom zitten in sommige eieren twee dooiers?
Distribution / Range
Hoe worden de kleuren en patronen van een eierschaal gevormd? Close Bolen , Bolen, G. Rothstein and C. Egg recognition in Yellow-billed and Black-billed Magpies in the absence of interspecific parasitism: Implications for parasite-host coevolution. Condor 2 Close Bolen et al. Currently there is considerable conservation concern about this species related to its vulnerability to West Nile virus Crosbie, S. Koenig, W. Reisem, V. Kramer, L. Marcus, R. Carney, E. Pandolfino, G. Bolen, L. Crosbie, D.
Bell and H.
Auk 3 Close Crosbie et al. Dominant forb species: No info. Ground cover: No info. Slope: No info.
Aspect: No info. Snags: No info. Distance to water: Permanent water natural or stock ponds generally within one km of nest. Other: Nests often located at end of vertical or horizontal branch devoid of side limbs. Elevation: No quantitative data. Habitat occurs mainly on the floor of the Central Valley and in the adjacent lower foothills of the Sierras and in valleys among Coast Ranges; generally below ft elevation.
Fragmentation: Extensive fragmentation and degradation of habitat has occurred and populations responses have varied geographically. Breeding populations in the Salinas Valley, Monterey County, and Santa Clara County appear to have declined or disappeared due to fragmentation. However, populations in fragmented areas near Sacramento and Davis have persisted Reynolds Patch size: No info.
Disturbance natural or managed : Populations may have been lost due to housing and agricultural development in oak savanna habitat. Effects of grazing or fire in oak savanna unknown. Generally thrives in grazed landscape, provided nesting habitat available. Direct persecution poisoning, shooting, harassing has decimated populations. Adjacent land use: Little info.
Breeding populations can be extirpated as a side-effect of rodent poisoning on adjacent lands Reynolds Dietary: Starvation in a major cause of nesting mortality, thus food supplies likely influence occurrence and population growth. Reynolds suggests that food availability during the breeding season and long summer drought is the most important regulator of populations. Sensitivity to human-induced disturbance: Direct persecution poisoning, shooting, harassing has decimated populations. Young will fledge prematurely if nests are disturbed and capture of adults and young and close monitoring on nests make birds more wary of humans Reynolds Pesticide use: Secondary and incidental poisoning by compound used in ground squirrel control programs has been documented, resulting in the extirpation of a breeding colony Koenig and Reynolds Population declines in the s linked to poisoning campaigns Linsdale Predators: Few direct observations.
Red-tailed Hawks and Golden Eagles take nestlings and fledglings. Predation on eggs also occurs but predators not identified. Population-level effects of predation are unknown. Reynolds estimated the minimum total population size for Yellow-billed Magpies to be 25,, breeding pairs. A recent estimate of overall population size based on extrapolation from BBS data was , individuals, which would make Yellow-billed Magpie the least abundant of California's endemic or near-endemic birds P. Blancher pers.
No evidence for deviation from sex ratio. Of nests monitored, Hatching success varies among years and starvation is a major cause of chick mortality. No more than one brood produced per year. Birds will re-nest after nest failure if failure occurs early in the breeding season; re-nesting takes place in a refurbished existing nest.
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Lifetime reproductive success uncertain due to long life span, but available data shows 1. Mean natal dispersal distance of the young that recruited into their natal colony was Many young likely disperse greater distances and females probably disperse farther than males. Habitat loss and alteration: Yellow-billed Magpies are dependent on the preservation of oak savanna habitat for their continued existence.
This habitat has been greatly reduced and is under current threat from housing development and intensified agriculture. Poisoning: Yellow-billed Magpies appear to be especially sensitive to harm from broadcast poisoning of ground squirrels with compound Such monitoring programs should focus on populations located near possible threats human development or poisoning programs.
The Magpies: The Ecology and Behaviour of Black-billed and Yellow-billed Magpies by Birkhead, T.r.
Research also is needed to better understand the habitat requirements for breeding colonies and the effects of habitat alteration on population persistence. BBS results suggest a fairly stable population in California as a whole, but there has been some reduction in range the loss of populations from the South Coast and southern San Joaquin Valley is based on historical data.
Entire breeding range of this species is within California.