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We estimated the statistical power of the first and last statistical test presented in 697 papers from 10 behavioral journals. First tests had significantly greater statistical power and reported more significant results (smaller p values) than did last tests. This trend was consistent across journals, taxa, and the type of statistical test used. On average, statistical power was 13--16% to detect a small effect and 40--47% to detect a medium effect. This is far lower than the general recommendation of a power of 80%. By this criterion, only 2--3%, 13--21%, and 37--50% of the tests examined had the requisite power to detect a small, medium, or large effect, respectively. Neither p values nor statistical power varied significantly across the 10 journals or 11 taxa. However, mean p values of first and last tests were significantly correlated across journals (r =.67, n = 10, p =.034), with a similar trend for mean power (r =.63, n = 10, p =.051). There is therefore some evidence that power and p values are repeatable among journals. Mean p values or power of first and last tests were, however, uncorrelated across taxa. Finally, there was a significant correlation between power and reported p value for both first (r =.13, n = 684, p =.001) and last tests (r =.16, n = 654, p

The costs to females of participating in extrapair copulations is an interesting but hitherto neglected topic in behavioral ecology. An obvious potential cost to females is male physical sanctions. However, although retaliation and punishment by male partners has been proposed as a basic cost for female extrapair behavior in theory, it has not been experimentally demonstrated. We studied the breeding biology of the lesser gray shrike (Lanius minor) and combined field observations and a field experiment to show that (1) there is a high intrusion rate during the female's fertile period, and extrapair copulations occur in this population; (2) by detaining females during the fertile phase, males were induced to retaliate physically against their partners, thereby increasing costs related to female extrapair behavior; and (3) there were no obvious costs to males of punishing their mates. DNA fingerprinting reveals that extrapair paternity is rare or absent in this population. Although we cannot conclude that monogamy at the genetic level is the result of male retaliation, we do show that male physical sanction is a cost that deceptive females have to assume. Males' strategies based on coercion should be considered when explaining variation in extrapair paternity across species. Copyright 2003.