Nest Defence and Evolution of Reversed Sexual Size Dimorphism in Snowy Owls Nyctea scandiaca

1983 ◽  
Vol 14 (1) ◽  
pp. 58 ◽  
Author(s):  
Christer G. Wiklund ◽  
Jimmy Stigh
Keyword(s):  
Sexual Size Dimorphism ◽  
Nest Defence ◽  
Size Dimorphism ◽  
Reversed Sexual Size Dimorphism

scholarly journals Why female birds of prey are larger than males

2020 ◽  
Vol 129 (3) ◽  
pp. 532-542
Author(s):  
Jonny Schoenjahn ◽  
Chris R Pavey ◽  
Gimme H Walter
Keyword(s):  
Sexual Size Dimorphism ◽  
A Priori ◽  
Nest Defence ◽  
Birds Of Prey ◽  
Causal Process ◽  
Size Dimorphism ◽  
Substantial Body ◽  
Key Factor ◽  
Reversed Sexual Size Dimorphism ◽  
Passionate Debate

Abstract The causes of the reversed sexual size dimorphism (RSD; females larger than males) in birds of prey are subject to a centuries-old, passionate debate. A crucial difficulty is to distinguish whether the postulated benefits derive from the proposed causal process(es) or are incidental. After reviewing the existing literature, we present a methodology that overcomes this difficulty and renders unnecessary any speculative a priori distinctions between evolved function and incidental effects. We can thus justify the following novel version of the well-known nest defence hypothesis as the most likely to explain the phenomenon in all birds of prey that show RSD: if the female predominates in actively defending the eggs and young against predators, then she is the heavier sex, and her relatively greater body mass is adaptive. That is, heavier females are favoured (independently of males) by natural selection. The attractiveness of this hypothesis is that it has the potential to explain the phenomenon in all raptors exhibiting RSD, can deal with the exceptional cases in this group, explains the direction of the dimorphism, focuses on a key factor in the reproductive success of most raptors, is parsimonious, i.e. does not require supporting hypotheses, and is supported by a substantial body of evidence.

Reversed Sexual Size Dimorphism and Parental Care: Minimal Division of Labour in the Blue-Footed Booby

Behaviour ◽  
1995 ◽  
Vol 132 (7-8) ◽  
pp. 479-496 ◽  
Author(s):  
Hugh Drummond ◽  
Maria Guerra
Keyword(s):  
Parental Care ◽  
Sexual Size Dimorphism ◽  
Division Of Labour ◽  
Avian Species ◽  
Nest Defence ◽  
Adult Size ◽  
Size Dimorphism ◽  
Behavioural Observation ◽  
Males And Females ◽  
Reversed Sexual Size Dimorphism

AbstractReversed sexual size dimorphism in avian species (females larger than males) may be an adaptive consequence of different roles of males and females in parental care. We examined the alleged division of labour in two-chick broods of the blue-footed booby, using behavioural observation and frequent weighing of chicks. In the first week of parental care, males and females fed broods at similar frequencies and provided similar masses of food, but females brooded more than males when broods were 5-10 d old. Subsequently, females provided a greater mass of food and frequency of feeds than males until chicks were at least 35 d old (mass) and 60 d old (frequency), while attending the brood for just as much time as males until chicks were at least 35 d old. Males and females did not differ in the tendency to feed (frequency and mass) the first-hatched chick differentially. In nearly all components of parental care examined here, and in other studies, the female's contribution is equal to or greater than the male's. Only in clutch attendance and nest defence does the male contribute more than the female, but his small size seems unlikely to enhance performance in these activities. Overall, small size appears potentially to limit male provisioning of the brood, and is unlikely to be an adaptation for division oflabour in parental care. This result casts doubt on the relevance of the division-of-labour hypothesis for adult size dimorphism.

scholarly journals Reversed sexual size dimorphism: body size patterns in sexes of lesser kestrels (Falco naumanni) in the Ikh Nart Nature Reserve, Mongolia

2019 ◽  
Vol 12 (3) ◽  
pp. 363-368 ◽  
Author(s):  
Onolragchaa Ganbold ◽  
Richard P. Reading ◽  
Ganchimeg J. Wingard ◽  
Woon Kee Paek ◽  
Purevsuren Tsolmonjav ◽  
...  
Keyword(s):  
Body Size ◽  
Sexual Size Dimorphism ◽  
Nature Reserve ◽  
Size Dimorphism ◽  
Falco Naumanni ◽  
Reversed Sexual Size Dimorphism

scholarly journals Structural complexity of hunting habitat and territoriality increase the reversed sexual size dimorphism in diurnal raptors

2018 ◽  
Vol 49 (10) ◽  
pp. e01745 ◽  
Author(s):  
Lorenzo Pérez-Camacho ◽  
Sara Martínez-Hesterkamp ◽  
Salvador Rebollo ◽  
Gonzalo García-Salgado ◽  
Ignacio Morales-Castilla
Keyword(s):  
Sexual Size Dimorphism ◽  
Structural Complexity ◽  
Size Dimorphism ◽  
Reversed Sexual Size Dimorphism

Evolution of Reversed Sexual Size Dimorphism in Skuas and Jaegers

The Auk ◽  
1999 ◽  
Vol 116 (1) ◽  
pp. 158-168 ◽  
Author(s):  
Paulo Catry ◽  
Richard A. Phillips ◽  
Robert W. Furness
Keyword(s):  
Sexual Size Dimorphism ◽  
Size Dimorphism ◽  
Reversed Sexual Size Dimorphism
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