Variation in weight and composition of Red-winged Blackbird eggs

1987 ◽  
Vol 65 (3) ◽  
pp. 605-607 ◽  
Author(s):  
Katherine E. Muma ◽  
C. Davison Ankney
Keyword(s):  
Total Energy ◽  
Breeding Season ◽  
Good Predictor ◽  
Molothrus Ater ◽  
Agelaius Phoeniceus ◽  
Egg Weight ◽  
Highly Correlated

To investigate variation in egg weight and composition we collected and analyzed 38 Red-winged Blackbird (Agelaius phoeniceus) eggs. The composition of Red-winged Blackbird eggs was very similar to that reported for Brown-headed Cowbird (Molothrus ater) eggs. Egg weight is a good predictor of total energy (kJ) in blackbird eggs as those two variables were highly correlated (r2 = 0.66). Weight of Red-winged Blackbird eggs did not change over the breeding season.

scholarly journals Variations in Calcium Use by Birds During the Breeding Season

The Condor ◽  
2001 ◽  
Vol 103 (3) ◽  
pp. 592-598 ◽  
Author(s):  
André A. Dhondt ◽  
Wesley M. Hochachka
Keyword(s):  
Breeding Season ◽  
High Frequency ◽  
Molothrus Ater ◽  
Egg Laying ◽  
Surprising Result ◽  
Very High Frequency ◽  
Cyanocitta Cristata ◽  
Egg Formation ◽  
Calcium Sources ◽  
Very High

Abstract During the breeding season birds need increased amounts of dietary calcium during egg laying and nestling rearing. Passerines acquire calcium shortly before and during laying and do not store calcium for egg formation. Many passerines need to eat extraneous calcium in the form of snail shells or calcareous grit to acquire the element. However, very little is known about variation in the dependency of birds on extraneous calcium, and where this calcium is acquired. Using reports from volunteers who provided extraneous calcium sources at feeder sites across North America we documented that (1) the use of extraneous calcium varied during the breeding season; (2) the location in which species preferentially took the calcium varied with typical feeding location, aside from swallows which, somewhat surprisingly, favored calcium offered on the ground; (3) Brown-headed Cowbirds (Molothrus ater) did not visit calcium sites more often than other blackbirds; (4) calcium use varied among species with thrushes, wrens, and woodpeckers taking calcium only rarely, and swallows, pigeons, and corvids taking calcium frequently. The most surprising result perhaps was the very high frequency of calcium use in jays; Blue Jays (Cyanocitta cristata) may hoard calcium in the fall. Variaciones en el Uso de Calcio por Aves durante la Época Reproductiva Resumen. En la época reproductiva, las aves necesitan incrementar la cantidad de calcio en la dieta durante el período de postura de huevos y cría de los pichones. Las aves paserinas adquieren calcio poco antes y durante la postura y no lo almacenan para la formación de los huevos. Muchas aves paserinas necesitan ingerir calcio de fuentes externas como conchas de caracoles o cascajo calcáreo para adquirir este elemento. Sin embargo, se sabe muy poco sobre la variación en el grado de dependencia de las aves de calcio externo y sobre dónde adquieren este calcio. Con base en reportes de voluntarios que suministraron fuentes externas de calcio en comederos a través de Norteamérica, documentamos que (1) el uso de calcio externo varió durante la época reproductiva; (2) el sitio en donde las especies tomaron el calcio preferencialmente varió de acuerdo al sitio típico de alimentación, con excepción de las golondrinas, que de manera algo sorprendente, prefirieron el calcio ofrecido en el suelo; (3) Molothrus ater no visitó sitios con calcio con más frecuencia que otros ictéridos; (4) el uso de calcio varió entre especies: los túrdidos, troglodítidos y carpinteros muy rara vez tomaron calcio, mientras que las golondrinas, palomas y córvidos lo hicieron frecuentemente. Quizás el resultado más sorprendente fue la muy alta frecuencia de uso de calcio en Cyanocitta; C. cristata podría acumular calcio durante el otoño para uso futuro.

Site selection and repeatability in Brown-Headed Cowbird (Molothrus ater) parasitism of Eastern Phoebe (Sayornis phoebe) nests

2001 ◽  
Vol 79 (8) ◽  
pp. 1518-1523 ◽  
Author(s):  
Mark E Hauber
Keyword(s):  
Reproductive Success ◽  
Breeding Season ◽  
Site Selection ◽  
Molothrus Ater ◽  
Structural Failure ◽  
Sayornis Phoebe ◽  
Eastern Phoebe ◽  
Site Discrimination

The reproductive success of obligate brood parasitic birds depends on their ability to seek out heterospecific nests. Some nests are more suitable for parasitism than others and, for example, parasitic females may benefit from laying eggs preferentially and repeatedly at safer sites. Observations on patterns of Brown-headed Cowbird (Molothrus ater) parasitism on Eastern Phoebes (Sayornis phoebe) across 2 years suggested that parasitism occurred at above chance levels during the first rather than the second nesting attempts and at nests located under eaves rather than bridges. Previously parasitized nests were more likely to be parasitized again in the subsequent breeding season. Sites under eaves and bridges did not differ in whether Brown-headed Cowbirds could be detected in the proximity of the nest. However, nests from first nesting attempts and nests under eaves were less likely to be lost as a result of structural failure of the Eastern Phoebe's mud nest. These data suggest that site discrimination by Brown-headed Cowbirds leads to adaptive patterns of parasitism among available Eastern Phoebe nests.

L-carnitine improves egg production in black neck ostriches

2008 ◽  
Vol 48 (10) ◽  
pp. 1341
Author(s):  
A. Hajibabaei ◽  
M. Shivazad ◽  
Sh. Golzar Adabi ◽  
A. Lavaf ◽  
N. Eila
Keyword(s):  
Fatty Acids ◽  
Breeding Season ◽  
Egg Production ◽  
Basal Diet ◽  
Control Group ◽  
Long Chain Fatty Acids ◽  
Egg Weight ◽  
Dietary Effects ◽  
Protein Sparing ◽  
Long Chain

The important functions of L-carnitine are fostering the oxidation of long-chain fatty acids by mitochondria and stimulating protein-sparing action by increasing energy derived from lipids. The present study was conducted to investigate dietary effects of L-carnitine on egg production of breeder ostriches. Ninety black neck ostrich breeder birds (60 females and 30 males) were examined randomly (completely randomised design) within three treatments and five replicates for 7 months in breeding season. A basal diet was formulated and used for the control group (L1), while two levels of L-carnitine, 250 mg/kg and 500 mg/kg, were included in the basal diet for treatments L2 and L3, respectively. The egg production percentage, egg weight and defective eggshell percentage were measured. The supplementary diet with 500 mg/kg L-carnitine increased (P < 0.01) the egg production percentage. Means (±s.e.) of egg production percentage for L1, L2 and L3 were 9.68, 12.95 and 17.13% (±1.08), respectively. L-carnitine had no effect on the egg weight and the defective eggshell percentage. The results suggest that basal diet supplemented with 500 mg/kg L-carnitine can increase the egg production percentage of ostriches.

The annual testicular cycle of the brown-headed cowbird (Molothrus ater)

1968 ◽  
Vol 46 (1) ◽  
pp. 77-87 ◽  
Author(s):  
D. M. Scott ◽  
A. L. A. Middleton
Keyword(s):  
Breeding Season ◽  
Molothrus Ater ◽  
Age Groups ◽  
Egg Laying ◽  
Sperm Production ◽  
Behavioral Differences ◽  
Testicular Regression ◽  
Old Adult ◽  
The Mean ◽  
Two Age Groups

An analysis of the spermatogenic condition and of the weights of testes from about 450 brown-headed cowbirds (Molothrus ater) was made to determine the annual cycle of this species at London, Ontario, and to ascertain variation in the cycle due to age. Testes of birds more than 1 year old (adult) reached maximal weights in late April and early May coincident with the beginning of egg-laying, and about 3 weeks before the testes of 1-year-old birds (yearlings) reached their maximal weight. The mean weights of testes of adults were usually greater, often significantly so, than those of yearlings. From about May 23 to June 23 there were no statistically significant differences in the weights of testes from the two age groups. Beginning in late June, the weights of testes declined rapidly in both age groups and reached a minimum in August. Minimal weights of testes persisted in captive birds until February.Large amounts of sperm were present in the testes of adults in mid-April and of yearlings in late April well in advance of maximal testicular weights. Sperm production occurred in most birds until early July but had ceased in most by late July.Testes, apparently undergoing regression, were noted significantly (p <.005) more frequently in adults than in yearlings in May and early June at the height of the breeding season. The significance of this observation and some aspects of testicular regression, previously unrecorded, are discussed. Adult birds are more sedentary than most yearlings in the breeding season and, unlike the latter, habitually associate with the same female. These behavioral differences may be related to the observed differences between the age groups in the testicular cycle.

The time of day of egg laying by the Brown-headed Cowbird and other icterines

1991 ◽  
Vol 69 (8) ◽  
pp. 2093-2099 ◽  
Author(s):  
David M. Scott
Keyword(s):  
Molothrus Ater ◽  
Time Of Day ◽  
Egg Laying ◽  
Agelaius Phoeniceus ◽  
Brood Parasite ◽  
Dendroica Petechia ◽  
Cardinalis Cardinalis ◽  
Vireo Olivaceus ◽  
Molothrus Bonariensis ◽  
Dumetella Carolinensis

I present data on the time of day of oviposition for 16 species of icterines to evaluate the idea that laying exceptionally early in the morning by the brood parasite, the Brown-headed Cowbird (Molothrus ater), is a specialization for parasitism. This cowbird, the earliest known layer among icterines, typically lays before sunrise (sunrise −9.14 ± 2.52 (SE) min, n = 36). Another brood parasite, the Shiny Cowbird (Molothrus bonariensis), also sometimes lays before sunrise. The best-known nonparasitic icterines, the Red-winged Blackbird (Agelaius phoeniceus) and the Common Grackle (Quisacalus quiscula), lay shortly after sunrise. Fragmentary records show that several other icterines lay within an hour or so after sunrise. Data are inadequate to conclude that early laying by Brown-headed Cowbirds has arisen as an adaptation for parasitism. The Brown-headed Cowbird at London, Ontario, lays earlier than most local passerines, as is shown by new data on oviposition by seven host species arranged in order of increasing lateness of oviposition: Agelaius phoeniceus, Dendroica petechia, Melospiza melodia, Cardinalis cardinalis, Vireo olivaceus, Dumetella carolinensis, and Turdus migratorius.

GENETIC SOURCES OF RESISTANCE TO BLACKBIRD PREDATION IN SUNFLOWER

1986 ◽  
Vol 66 (1) ◽  
pp. 19-23 ◽  
Author(s):  
DAN E. PARFITT ◽  
GREGORY J. FOX
Keyword(s):  
Agelaius Phoeniceus ◽  
Narrow Sense ◽  
Sources Of Resistance ◽  
Bird Predation ◽  
Narrow Sense Heritability ◽  
The Third ◽  
Naturally Occurring ◽  
Xanthocephalus Xanthocephalus ◽  
Sib Families ◽  
Highly Correlated

Fifty-one sunflower (Helianthus annuus L.) inbreds were grown at three environments (locations) in North Dakota. Inbreds at two locations were subjected to naturally occurring bird predation by redwinged blackbirds (Agelaius phoeniceus L.) and yellowheaded blackbirds (Xanthocephalus xanthocephalus Bonaparte). The third sunflower plot was surrounded by a cage into which redwinged blackbirds were introduced. Bird damage was estimated as percent achenes removed from individual sunflower heads. Significant differences among environments were observed (P < 0.01). However, genotype performance among environments was highly correlated (P < 0.01). Half sib progeny from 36 of these inbreds were grown along with their maternal inbred parents to estimate narrow sense heritability (h2NS) of resistance to bird predation. Estimates of h2NS obtained by parent offspring regression and by covariance among half-sib families were h2NS = 0.69 and h2NS = 0.66, respectively. These estimates indicate a 67% level of heritability for resistance to bird predation, and suggest that it should be possible to develop sunflower lines with improved resistance.Key words: Sunflower, bird feeding, redwinged blackbird, yellowheaded blackbird

Reactions of Four Passerine Species To Threats of Predation and Cowbird Parasitism: Enemy Recognition or Generalized Responses?

Behaviour ◽  
1992 ◽  
Vol 123 (1-2) ◽  
pp. 84-105 ◽  
Author(s):  
Spencer G. Sealy ◽  
Diane L. Neudorf
Keyword(s):  
Host Species ◽  
Molothrus Ater ◽  
Egg Laying ◽  
Agelaius Phoeniceus ◽  
Bombycilla Cedrorum ◽  
Cowbird Parasitism ◽  
Dumetella Carolinensis ◽  
Passerella Iliaca ◽  
Enemy Recognition ◽  
Defensive Behaviours

AbstractFour host species of the parasitic brown-headed cowbird (Molothrus ater) were exposed to taxidermic mounts of a female cowbird, fox sparrow (Passerella iliaca), and common grackle (Quiscalus quiscula) at their nests during their egg-laying or nestling stage. Red-winged blackbirds (Agelaius phoeniceus), a species that accepts cowbird eggs laid in their nests, responded more aggressively to cowbird models early in their nesting cycle, indicating that they recognized the unique threat the cowbird posed. Gray catbirds (Dumetella carolinensis), northern orioles (Icterus galbula), and cedar waxwings (Bombycilla cedrorum) can remove cowbird eggs from their nests and for the most part they responded similarly to cowbird models and the "nonthreatening control," i.e. a fox sparrow. Cedar waxwings were nonaggressive to all the models and may rely on concealment to protect their nests from enemies. Removal of cowbird eggs by puncture ejection is more risky than grasp ejection. Despite this, orioles and waxwings (puncture ejectors) were not significantly more aggressive to cowbird models at egg laying than catbirds (grasp ejectors). Responses of the three rejector species toward the cowbird model did not change over the nesting cycle, indicating further that they do not recognize cowbirds as a unique threat. Rejector species may not recognize cowbirds because they have little experience with them. With the exception of waxwings, all of the hosts recognized the grackle as an enemy and increased their levels of defence from the laying to nestling stages. Three of the host-species did not simply respond in a generalized manner to any intruder at their nests but indeed recognized specific enemies. Considerable interspecific variability exists amongst the four species in defensive behaviours, which may reflect their different nesting habitats.

The Laying Cycle of Brown-Headed Cowbirds: Passerine Chickens?

The Auk ◽  
1983 ◽  
Vol 100 (3) ◽  
pp. 583-592 ◽  
Author(s):  
D. M. Scott ◽  
C. Davison Ankney
Keyword(s):  
Clutch Size ◽  
Breeding Season ◽  
Molothrus Ater ◽  
Short Interval ◽  
Gallus Gallus ◽  
Reproductive Period ◽  
Southern Ontario

Abstract We collected 270 female Brown-headed Cowbirds (Molothrus ater) in southern Ontario in 1976 to determine ovarian and oviducal growth during the breeding season and 188 female cowbirds in 1977 to estimate clutch size and the interval between clutches. Ovaries and oviducts grew rapidly in April, reached breeding size in early May, and remained at this size, without regression between clutches, until the end of the breeding season in early July. Ovaries and oviducts then regressed rapidly and by the end of July weighed about the same as those in early April. The clutch size averaged about 4.0-4.6 eggs, similar to clutch sizes of nonparasitic icterids. It varied greatly from 1 egg, in about 10% of the birds, to about 7 eggs. Two days without laying usually separated consecutive clutches, but some birds appeared to miss laying for only 1 day. Although atresia of large yolky follicles was common in birds between clutches, it did not always precede the end of a clutch. The long reproductive period without regression and the short interval between clutches are atypical of passerine reproduction. Rather, the laying cycle of cowbirds is similar to that of domestic chickens (Gallus gallus). The laying cycle of cowbirds seems adapted to a continuous supply of host nests; atresia may be related to a shortage of nests.

Estimation of genetic parameters of growth and egg production traits by animal model in IWK layer strain

2019 ◽  
Author(s):  
P. Chandan ◽  
T.K. Bhattacharya ◽  
U. Rajkumar ◽  
L.L.L. Prince ◽  
R.N. Chatterjee
Keyword(s):  
Animal Model ◽  
Body Weight ◽  
Egg Production ◽  
Heritability Estimate ◽  
The Body ◽  
Production Traits ◽  
Economic Traits ◽  
Egg Weight ◽  
Egg Number ◽  
Highly Correlated

Indian White Leghorn strain-IWK has been improved for higher egg weight as well as number over last twelve generations at ICAR-Directorate of Poultry Research, Hyderabad. The data collected on various economic traits of egg production were analyzed using REML approach of animal model. Current study showed that the heritability estimate of body weight, age at sexual maturity (ASM), egg numbers and egg weight was moderate to high, low to moderate, low and high, respectively. The body weight was positively correlated with egg weight but negatively correlated with egg numbers. The body weight at 16 and 20 weeks were negatively correlated with ASM and were very important for achieving early ASM. ASM was negatively correlated with egg numbers. The egg weight regressed as the egg number increased. The part period egg production EP52 was highly correlated with EP64; therefore EP52 can be used for selecting parents for higher egg number instead of EP64.

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