The onset and duration of fertility in the American kestrel

1976 ◽  
Vol 54 (9) ◽  
pp. 1595-1597 ◽  
Author(s):  
David M. Bird ◽  
Roger B. Buckland
Keyword(s):  
Sperm Storage ◽  
Falco Sparverius ◽  
American Kestrel ◽  
Egg Formation ◽  
American Kestrels

Eight American kestrels (Falco sparverius) were artificially inseminated once and their eggs removed one by one to determine the onset and duration of fertility. A mean duration of fertility of 8.1 days, ranging from 4 to 12 days, suggests the presence of sperm storage glands in this species. The fact that fertile eggs can appear 48 h after insemination indicates that onset of fertility is at most 1 day, allowing for 1 day of egg formation.

The influence of Trichinella pseudospiralis infection on the behaviour of captive, nonbreeding American kestrels (Falco sparverius)

1988 ◽  
Vol 66 (7) ◽  
pp. 1685-1692 ◽  
Author(s):  
Michèle D. Saumier ◽  
Manfred E. Rau ◽  
David M. Bird
Keyword(s):  
Falco Sparverius ◽  
Competitive Fitness ◽  
American Kestrel ◽  
Behavioural Changes ◽  
Trichinella Pseudospiralis ◽  
Behavioural Effects ◽  
American Kestrels ◽  
Muscle Larvae ◽  
Adult Phase ◽  
Muscle Groups

Trichinella pseudospiralis infections induced mild behavioural changes in the American kestrel host (Falco sparverius) within the first 5 days postinoculation, a period that corresponds to the adult phase of the infection. However, more severe effects on mobility were precipitated as the larvae migrated and became established in the musculature. The debilitation persisted for at least 5 weeks postinoculation and involved a reduction in exercising, flying, elevated perching, and preening, and was accompanied by an increase in the frequency of walking and floor perching. Such behavioural effects, attributable to the presence of muscle larvae, may reduce the competitive fitness of infected individuals. The muscle larvae were randomly distributed among various muscle groups.

scholarly journals Covariation of Clutch Size, Laying Date, and Incubation Tendency in the American Kestrel

The Condor ◽  
2001 ◽  
Vol 103 (3) ◽  
pp. 570-578 ◽  
Author(s):  
Keith W. Sockman ◽  
Hubert Schwabl
Keyword(s):  
Environmental Factors ◽  
Clutch Size ◽  
Egg Production ◽  
Laying Date ◽  
Falco Sparverius ◽  
Free Living ◽  
American Kestrel ◽  
Proximate Mechanisms ◽  
American Kestrels ◽  
Seasonal Decline

Abstract Seasonal decline in clutch size is common in birds, but the proximate mechanisms for this phenomenon have not been elucidated. The most credible model to date posits that late-laying females lay fewer eggs due to a seasonal increase in the tendency to incubate during laying, which inhibits egg production. We tested this model with free-living and laboratory American Kestrels (Falco sparverius) by quantifying changes in clutch size and incubation tendency during laying over the course of the breeding phase. Consistent with the model, clutch size in free-living kestrels decreased while incubation increased with progress of the 74-day breeding phase. Inconsistent with the model, variation in incubation tendency during laying was not associated with clutch size in either the field or the laboratory. In the laboratory, incubation increased but clutch size did not decrease over the course of the 77-day breeding phase. In the laboratory, females that nested early in one breeding phase renested more quickly and nested in a second breeding phase more quickly than females nesting late in the first breeding phase. This indicates that timing of laying is, in part, a property of individual females, independent of environmental factors. Together, our findings suggest that both clutch size and timing of laying are inherent, correlated properties of particular females. Although incubation tendency may influence clutch size, other factors appear to override its influence. Covariación del Tamaño de la Nidada, la Fecha de Postura y la Tendencia de Incubación en Falco sparverius Resumen. Aunque la disminución estacional en el tamaño de la nidada es común entre las aves, los mecanismos proximales para este fenómeno no han sido elucidados. El modelo de mayor credibilidad propuesto hasta el momento sugiere que las hembras que ovipositan tarde ponen menos huevos debido a un aumento estacional en la tendencia a incubar durante la postura que inhibe la producción de huevos. Pusimos a prueba este modelo con individuos de Falco sparverius en condiciones naturales y en cautiverio, cuantificando los cambios en el tamaño de la nidada y la tendencia a incubar durante la postura a lo largo de la época reproductiva. Tal como el modelo plantea, el tamaño de la nidada en individuos silvestres de F. sparverius disminuyó mientras que la incubación aumentó a medida que transcurrían los 74 días de la época de reproducción. Mientras tanto, en contraste con el modelo, la variación en la tendencia a incubar durante la postura no estuvo asociada con el tamaño de la nidada ni en el campo ni en el laboratorio. En el laboratorio, la incubación aumentó pero el tamaño de la nidada no disminuyó en el transcurso de la época reproductiva (77 días). En condiciones de laboratorio, las hembras que anidaron temprano en una fase reproductiva volvieron a anidar más rápidamente en una segunda fase que las hembras que anidaron tarde en la primera. Esto indica que el tiempo en que se hace la postura es en parte una propiedad de cada hembra y es independiente de factores ambientales. En conjunto, nuestros hallazgos sugieren que tanto el tamaño de la nidada como el momento de la postura son propiedades correlacionadas de cada hembra en particular. Aunque la tendencia a incubar podría influenciar el tamaño de la nidada, otros factores parecen anular su influencia.

The Development of Prey Recognition and Predatory Behaviour in the American Kestrel Falco Sparverius

Behaviour ◽  
1974 ◽  
Vol 49 (3-4) ◽  
pp. 313-324 ◽  
Author(s):  
Helmut C. Mueller
Keyword(s):  
Mouse Models ◽  
Minor Role ◽  
Falco Sparverius ◽  
Predatory Behaviour ◽  
Tissue Paper ◽  
American Kestrel ◽  
Prey Recognition ◽  
American Kestrels ◽  
A Minor ◽  
Live Mouse

AbstractNine hand-reared American kestrels were exposed to a series of objects, stationary and moving, ranging from a tissue-paper ball, a crude tissue-paper mouse, through stuffed and dead mice, and finally live mice. Only one bird responded consistently to paper models, and only to moving mouse-models. All birds attacked live mice, including five that had not responded to models or dead mice. Two of the five inexperienced birds attacked their first live mouse in less than 10 sec. Attacks on paper models were desultory and disoriented and are believed to represent play rather than predatory behaviour. Attacks on live mice were intense, rapid, sustained and well-oriented, with the mouse being grasped by the thorax, neck or head and biting directed to the head or neck. Eight of nine birds attacked their first mouse (live, dead, or stuffed) expertly and all nine birds achieved consistent, expert perfonnance in less than six trials. The inference is drawn that experience plays a minor role in the development of recognition, capturing and killing of mice by kestrels.

Nestling growth and fledging success in manipulated American kestrel broods

1992 ◽  
Vol 70 (12) ◽  
pp. 2421-2425 ◽  
Author(s):  
Nicholas W. Gard ◽  
David M. Bird
Keyword(s):  
Clutch Size ◽  
Growth Rates ◽  
Brood Size ◽  
Wild Birds ◽  
Falco Sparverius ◽  
Nestling Growth ◽  
American Kestrel ◽  
Fledging Success ◽  
American Kestrels ◽  
Parental Ability

To study factors regulating clutch size in American Kestrels (Falco sparverius), brood manipulation experiments were performed on captive and wild birds in southwestern Quebec during 1986 and 1987. The largest normally occurring brood size was 5 young. Manipulations enlarged or decreased broods to 7 or 2 young, respectively. Significantly more young fledged from wild control and enlarged broods in 1987 than from comparable groups in 1986. The average number of young fledging from enlarged wild broods in 1987 was slightly higher than for control broods, but fledging weight was significantly depressed in enlarged broods. Growth rates and tarsal and antebrachial length at fledging were not affected by brood size, but development of primary feathers was slower in enlarged wild broods. Parental ability to adequately feed all young appears to be the major factor limiting brood size in American Kestrels.

Energetic consequences of sex-related habitat segregation in wintering American kestrels (Falco sparverius)

2002 ◽  
Vol 80 (3) ◽  
pp. 516-523 ◽  
Author(s):  
Daniel R Ardia
Keyword(s):  
Body Condition ◽  
Habitat Segregation ◽  
Net Energy ◽  
Falco Sparverius ◽  
American Kestrel ◽  
Energy Expenditures ◽  
American Kestrels ◽  
Habitat Differences ◽  
Daily Energy ◽  
Behavioural Dominance

Behavioural dominance can cause individuals to use less-preferred habitats, with potentially important life-history consequences. In the American kestrel, Falco sparverius, females exclude males from preferred open areas; I hypothesized that this sex-related habitat segregation leads to energetic consequences for males. I predicted that males would show decreased body condition over winter, while females would not, and that females would maintain larger net-energy surpluses than would males. Working in southeastern Pennsylvania, between 1991 and 1995, I conducted 150 behavioural observations and measured body condition of 235 wintering kestrels. Male kestrels maintained a lower body condition (residuals of a regression of mass vs. size) than did females and showed a decrease in mean body condition over winter, which females did not. I estimated that females had larger daily energy expenditures than did males (248 vs. 195 kJ per bird per day, ratio 1.27) but also had larger daily energy intakes (537 vs. 322 kJ/day, ratio 1.67). Females had larger net energy surpluses than did males (288 vs. 126 kJ/day, ratio 2.27), particularly when temperatures were <0°C. I conclude that differences in energetics are due in part to habitat differences and that males may suffer consequences by being forced to use less-preferred habitats.

scholarly journals The American Kestrel (Falco sparverius) genoscape: implications for monitoring, management, and subspecies boundaries

The Auk ◽  
2021 ◽  
Author(s):  
Kristen C Ruegg ◽  
Michaela Brinkmeyer ◽  
Christen M Bossu ◽  
Rachael A Bay ◽  
Eric C Anderson ◽  
...  
Keyword(s):  
United States ◽  
Population Structure ◽  
The United States ◽  
Falco Sparverius ◽  
Long Distance ◽  
American Kestrel ◽  
Sampling Locations ◽  
American Kestrels ◽  
Outlier Loci ◽  
The U.S

AbstractIdentifying population genetic structure is useful for inferring evolutionary process and comparing the resulting structure with subspecies boundaries can aid in species management. The American Kestrel (Falco sparverius) is a widespread and highly diverse species with 17 total subspecies, only 2 of which are found north of U.S./Mexico border (F. s. paulus is restricted to southeastern United States, while F. s. sparverius breeds across the remainder of the U.S. and Canadian distribution). In many parts of their U.S. and Canadian range, American Kestrels have been declining, but it has been difficult to interpret demographic trends without a clearer understanding of gene flow among populations. Here we sequence the first American Kestrel genome and scan the genome of 197 individuals from 12 sampling locations across the United States and Canada in order to identify population structure. To validate signatures of population structure and fill in sampling gaps across the U.S. and Canadian range, we screened 192 outlier loci in an additional 376 samples from 34 sampling locations. Overall, our analyses support the existence of 5 genetically distinct populations of American Kestrels—eastern, western, Texas, Florida, and Alaska. Interestingly, we found that while our genome-wide genetic data support the existence of previously described subspecies boundaries in the United States and Canada, genetic differences across the sampled range correlate more with putative migratory phenotypes (resident, long-distance, and short-distance migrants) rather than a priori described subspecies boundaries per se. Based on our results, we suggest the resulting 5 genetically distinct populations serve as the foundation for American Kestrel conservation and management in the face of future threats.

Reproductive changes in American kestrels (Falco sparverius) in relation to exposure to technical hexabromocyclododecane flame retardant

2011 ◽  
Vol 30 (11) ◽  
pp. 2570-2575 ◽  
Author(s):  
Kim J. Fernie ◽  
Sarah C. Marteinson ◽  
David M. Bird ◽  
Ian J. Ritchie ◽  
Robert J. Letcher
Keyword(s):  
Flame Retardant ◽  
Falco Sparverius ◽  
American Kestrels
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