Table 1.
Explanatory variables for individual and environmental effects on lifetime reproduction (LR) of northern goshawks in Arizona, USA.
Table includes variable name and variable description for generalized linear models.
Table 2.
Life history characteristics of breeding goshawks.
Mean±SE and median (range) of age at first breeding, lifespan, breeding lifespan (first to last breeding year), number of breeding attempts, and lifetime production (LR) of fledglings of 164 (69 known-age plus 95 ≥4-years-old) male and female northern goshawks first breeding in the 1992–2000 cohorts in Arizona, USA.
Fig 1.
Number of goshawks by lifespan of known-age males and females.
Lifespan of 28 male and 41 female northern goshawks of known-age (banded as nestlings or aged 2- or 3-years-old based on plumage at first breeding) northern goshawks first breeding in the 1992‒2000 cohorts of breeders in Arizona, USA, 1991–2010.
Fig 2.
Breeding lifespans (years from first to last breeding) of 75 males and 89 females of combined known-age and ≥4-year-old goshawks first breeding in the 1992‒2000 cohorts in Arizona, USA.
Fig 3.
Number of fledglings produced by goshawks during their lifetimes.
Individual lifetime reproduction (LR) of 75 males and 89 females of combined known-age and ≥4-year-old goshawks first breeding in the 1992‒2000 cohorts in Arizona, USA.
Table 3.
Number of individuals by age (number of full years since hatch) at first breeding (%) for 58 male and 88 female northern goshawks of known-age in Arizona, USA, 1991–2010.
Fig 4.
Annual percent of breeders that were 2-years-old was a function of a year’s quality for breeding.
Annual percent of breeders that were 2-years-old as a function of the quality of a breeding year (estimated as the percent of territories with egg-laying pairs; [77]) of northern goshawks in Arizona, USA. Monotonic increases in the recruitment of 2-year-old breeders indicated improving breeding conditions and the existence of vacancies on territories following periods of poor breeding.
Fig 5.
Age-specific reproduction by known-age goshawks.
Means, ±2 standard errors, and overall mean values (horizontal dashed line) of the raw data from GAMM analyses of age-specific reproduction by known-age male and female northern goshawks in Arizona, USA. Numbers below standard error bars indicate the number of males and females in each age group. (A) nest success (fledged ≥1 young) as a function of age of 164 breeding attempts by 58 males and 249 attempts by 88 females, (B) fledgling production as a function of age in 164 breeding attempts by 58 males and in 249 attempts by 88 females (population-level analyses), and (C) changes in numbers of fledglings produced in 85 breeding attempts by 40 males and 133 breeding attempts by 55 females that bred in one and the next year (individual-level analyses).
Fig 6.
Age-specific reproduction by goshawks aged ≥4-years-old at first breeding.
Means, ±2 standard errors, and overall mean values (horizontal dashed line) of raw data from the GAMM analyses of age-specific reproduction by male and female northern goshawks assigned a minimum age of ≥4-years old at their first breeding attempt in Arizona, USA. Numbers below standard error bars indicate the number of males and females in each age group. (A) nest success (fledged ≥1 young) as a function of age in 428 breeding attempts by 137 males and 491 attempts by 162 females, (B) fledgling production as a function of age in 428 attempts by 137 males and 491 attempts by 162 females (population-level analyses), and (C) changes in numbers of fledglings produced in 244 attempts by 107 individual males and in 266 attempts by 119 females that bred in one and the next year (individual-level analyses).
Fig 7.
Year effect on fledgling production by goshawks.
Expected year effect on fledgling production in 740 breeding attempts by 250 female (combined known-age and hawks aged ≥4-year-old on first breeding) northern goshawks from Poisson GAMM of population-level analysis of age-specific reproduction in Arizona, USA. The y-axis shows the deviation from the mean response and the shaded region depicts the 95% CI. The expected year effect on fledgling production by male goshawks (592 attempts by 195 males) was nearly identical to the female response.
Table 4.
Life history characteristics of goshawks first breeding at ages 2-, 3-, and 4+-year-olds.
Tukey multiple comparisons of mean (± 95% CI) lifespans (years), breeding lifespans (years), number of breeding attempts, nest failure rates, and lifetime reproduction (LR) for 164 first breeding at ages 2-, 3-, and 4+-year-olds (4-year and older known-age + ≥4-years-old) goshawks in the 1992‒2000 cohorts in Arizona, USA.
Fig 8.
Is mate choice based on mate age?
(A) Mate age composition of 37 pairings (33 males, 32 females) of known-age hawks, and (B) mate age composition of 169 pairings (120 males, 139 females) of hawks aged ≥4-year-old (including their known-age mates where relevant) in the year of pair formation by northern goshawks on the Kaibab Plateau, Arizona, USA. Size of dots indicates numbers of pairs observed in each mate-age category. Solid lines depict one-to-one relationships.
Fig 9.
Is mate choice based on a mate’s breeding experience?
Box plots of pair age differences in the year of pair formation with respect to a mate’s breeding experience by northern goshawks in Arizona, USA. Vertical bars are medians (i.e., 50th percentile), boxes contain the central 50% of differences (i.e., bounded by the 25th and 75th percentiles), and dots are outliers. “Both recruits” pairs are both first-time breeders, “recruit/exp” pairs are male recruit/female experienced, “exp/recruit” pairs are male experienced/female recruit, and “both exp” pairs are both previous breeders. (A) Known-age hawks only and (B) hawks aged ≥4-years-old with their known-age mates where relevant.
Fig 10.
(A) Variation in ages of pairs over time and fledgling production in all breeding attempts by pairs of different age compositions. Variation in age composition and fledgling production through the duration of pair bonds (not limited to initial year of pair formation) in 505 breeding attempts by 168 male and 180 female northern goshawks (known-age + ≥4-years-old hawks). Size of dots indicates numbers of pairs observed in each mate-age category. (B) heat map of maximum number of fledglings produced in each breeding attempt by pairs of mixed ages, and (C) heat map of mean number of fledglings produced in these breeding attempts in Arizona, USA. Gray-scale indicates the maximum number of fledgling (includes 0 fledglings) produced by pairs in each mate-age composition category; white areas indicate no data.
Fig 11.
Is mate choice based on mate size or physiological condition?
Scatter plot of z-scores for paired male and female goshawks showing (A) body mass and (B) heat map of the smoothed total number of fledglings per pair in 423 breeding attempts (not limited to initial year of pair formation) by 147 male and 151 female goshawks of known-mass on the Kaibab Plateau, Arizona, USA. Solid lines depict one-to-one relationships.
Table 5.
Influence of individual and environmental effects on lifetime reproduction (LR) of goshawks.
Slope parameter estimates from the generalized linear model candidate set with morphological data (tarsom, wingC, mass, and tail) included. Shown is adjusted standard error (), relative importance, and p-values for the model terms for the influence of individual and environmental effects on lifetime reproduction of 65 male and 86 female northern goshawks in Arizona, USA.
Fig 12.
Proportion of total fledglings and F1 recruits produced by varying proportions of individual breeders.
Proportional variation among 195 male and 250 female goshawks in total fledgling production and number of recruits to the local breeding population in Arizona, USA. Although 189 (96.4%) males and 238 (95%) females fledged young (lower curve), only 52 (27%) males and 71 (28%) females produced fledglings that recruited into the local breeding population (upper curve).
Fig 13.
Number of children and grandchildren that locally recruited as breeders in relation to the number of fledglings produced by individual male and female goshawks.
Number of banded descendants of 196 male (A, B) and 250 female (C, D) northern goshawks that recruited into the local breeding population as children (F1 generation) and grandchildren (F2 generation) in relation to the number of fledglings each breeder produced in Arizona, USA. Each ‘x’ represents an individual adult. Trend lines determined with Poisson regression with log-link functions.
Table 6.
No differences in the proportion of 2- or 3-years-old breeders in the less productive than more productive territories.
Fig 14.
Breeding goshawks occupied territories non-randomly.
Observed versus expected (from Poisson distribution) pattern of occupancy of 79 territories over 20 years by northern goshawks in Arizona, USA.
Fig 15.
Total fledglings produced by goshawks on 79 territories monitored at least 18 years in Arizona, USA.
Fig 16.
The number of unique breeders on a territory in relation to frequency of territory-specific occupancy and total fledgling production.
(A) Numbers of sequential breeding male and female goshawks on each of 36 territories monitored for 20 years in relation to (A) the number of years each territory had breeders, and in relation to (B) the 20-year total fledglings produced on each of the 36 territories in Arizona, USA.
Fig 17.
Are fewer fledglings per breeding attempt produced on less productive (low quality?) territories than on more productive (high quality?) territories?
Linear regressions of mean numbers of fledglings produced per breeding attempt on low productivity vs. high productivity territories and the sum total fledglings produced by 3 different cohorts of territories (36 territories monitored 20 years [1991‒2010]; 25 territories monitored 19 years [1992–2010]; and 18 territories monitored 18 years [1993–2010]) by northern goshawks in Arizona, USA. Territories in each cohort are divided into 4 quadrants based on their mean total fledglings produced per study period (vertical line) and means of numbers of fledglings produced per breeding attempt (horizontal line). Means (±SE) and ranges of numbers of years that territories were active (A; eggs laid), and means (±SE) and ranges of nest failures (F) are provided for each quadrant.
Fig 18.
Variation in annual fledgling production and goshawk breeding density contradicts the ideal pre-emptive model.
Contrary to predictions from the ideal pre-emptive model of habitat selection wherein the annual coefficient of variation (CV) in annual fecundity increases with breeder density as more lower quality territories become occupied and produce fewer and fewer young, the CV of annual fledgling production declined as breeding density increased (percent of territories with breeders; see inset) increased in Arizona, USA.