1 16 THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 1. March 2012 
Open Grass Shrub 
O 
O 
Forb 
FIG. I. Percent vegetative cover at random locations 
(white boxplots, n = 80) and Common Nighthawk nests (gray 
boxplots, n = 8 .) on Joint Base McGuire-Dix-Lakehurst, New 
Jersey. USA, in 2010. Open ground included bare sand, 
lichens, and matted dead vegetation (litter). Boxplots show 
median, interquartile range, and range of data. Open circles 
show points >1.5 interquartile ranges above the median. 
similar in 2009 and 2010 (Wilcoxon rank sum 
tests, IV = 24-43. P > 0.26), but 2010 nests 
diftered from vegetation at random locations 
(Fig. 1, Table I). Nest sites in 2010 had more 
open ground, shorter vegetation, shallower litter, 
and less grass and shrub cover than random areas' 
Nesting Phenology.—We estimated initiation 
dates for 16 of the 20 nests. Four were found 
during egg-laying, two were estimated based on 
a known hatch date, seven from an estimated 
hatch date, and three from the estimated age 
of young. The median nest initiation date was 
31 May with an interquartile range of 25 May to 
11 June, and a range of 18 May to 28 June 
(Fig. 2). One nest for which we could not 
accurately estimate initiation date was estab¬ 
lished prior to 17 May, as it was discovered with 
a two-egg clutch on this date. 
120 1 40 160 180 
Julian date 
FIG. 2. Estimated initiation dates (first egg Iaidi for 
Common Nighthawk nests monitored on Joint Base 
McGuire-Dix-Lakehurst, New Jersey. USA, in 20n° 
2010. Bins are in increments of 5 days, beginning on I' 
May (Julian day 135). Boxplot above shows median, 
interquartile range, and range of dates. Asterisks indican 
the average start and end dates for nest searches in 200 ' 
and 2010 . 
DISCUSSION 
The lack of data on breeding biology toi 
nightjars is a significant obstacle to effective 
conservation planning. This is especially relevant 
in North America as several species appear to I 
experiencing long-term population declines 
(Wilson 2008, Nebel et al. 2010. Sauer el al 
2011). We found nest survival through incubati"’ 
to be 79% (0.987 daily survival) which b 
considerably higher than reported by Perkins anJ 
Vickery (2007) in Florida (28%, 0.932 daily 
survival, n = 14 nests). Sample sizes for both 
studies were somewhat lower than those general 
recommended for daily survival rate estimation 
* SE) “ Comm °" nest sites ( 2009 - 2010 ) *1 - 
Wilc„r„ raTs U m fLr^ n 1 P '°‘ S “ J ° inl Bs “ McGttinr-Dix-Lakehurst. New Jersey. USA. 
- af e displayed between the columns: ns, P > 0.05; *, 0.05 > P > 0.01: **, 0.01 >P >(> ' 
_Y e g- height (cm) 
% Open 
% Grass 
% Forb 
% Shrub 
Litter depth (cm) 
Nests 2009 (« = 9) 
8.6 ± 3.3 
53.9 ± 7.9 
2LO ± 3.7 
7.8 ± 4.3 
6 -7 ± 3.4 
Nests 2010 (n = 8) 
ns 
ns 
ns 
ns 
ns 
9.7 ± 1.8 
63.1 ± 4.8 
14.4 ± 3.5 
10.6 ± 7.0 
12.5 ± 5.6 
0.3 ± 0.1 
** 
** 
* 
ns 
Random 20l0^jjy_ 
21.5 114 
31 . 8-24 
40.4 - 3-0 
3.1 i 1° 
29.1 t 3.0 
1.2 1 0-1 
