Nebraska Bird Review 
11 
because the feather tracts do not 
all begin growing on the same day. 
Index values were higher for growth 
of Redwing feather tracts, similar 
to the findings on the other growth 
data when compared to Goldfinches. 
The alar tracts develop faster than 
other tracts in both the Redwing and 
Goldfinch. 
It is interesting to note that Gold¬ 
finches can usually sustain flight 
for several feet when leaving the 
nest by 12.3 days of age while Red¬ 
wings can fly very little when leav¬ 
ing the nest on day 9.5. The pri¬ 
maries of the Redwings are about 40 
mm long when they leave the nest, 
but they weigh about 30 grams. Gold¬ 
finch fledglings have primaries 
about 30 mm long when they leave 
the nest, and they weigh about 11.5 
grams. Although it is difficult to 
compare wing surface area between 
new fledglings of Redwings and 
Goldfinches, it is obvious that Gold¬ 
finches have at lease one-half as 
much wing surface to support a 
little over a third as much weight 
as Redwing nestlings. One of the 
reasons for the better ability of the 
Goldfinch to fly is obviously due to 
their larger wing surface to weight 
ratio. 
c. Frequency of defecation in nest¬ 
lings. The percent of birds eliminat¬ 
ing wastes at least once when the 
nests were visited are given in Table 
7. These data are interesting for per¬ 
haps four reasons: 1) the frequency 
of defecation may indicate the quan¬ 
tity of food which the nestlings are 
receiving, 2) the frequency of defe¬ 
cation may indicate the period of 
fastest growth, 3) defecation may re¬ 
sult from the exercise of handling 
young and from a fright reaction of 
young as they grow older, and 4) a 
diet change may take place through¬ 
out the nestling period which may 
influence the percentage of digestible 
nutrients. 
TABLE 7 
GOLDFINCH NESTLING 
EYE OPENING AND DEFECATION 
Eye Percent 
Opening Defecating 
Day 
N 
Mean Value* 
N 
Percent 
0 
68 
- 
68 
15 
1 
63 
- 
62 
8 
2 
63 
0.2 
63 
16 
3 
59 
0.8+0.1 
57 
19 
4 
47 
1.1+0.1 
47 
34 
5 
36 
2.2+0.2 
36 
92 
6 
33 
3.2+0.2 
32 
97 
7 
40 
4.0±0.1 
39 
100 
8 
- 
- 
40 
100 
9 
- 
- 
40 
98 
10 
- 
- 
33 
100 
11 
- 
- 
25 
100 
12 
- 
- 
15 
100 
13 
- 
- 
5 
100 
A 0 
Not 
open 
1 Cracking open 
2 Half open 
4 Open 
Although it is known that nest¬ 
lings receive more food as they grow, 
their mean weight gain is more 
rapid when they are younger. The 
percentage of birds defecating when 
handled may be a good indication of 
when they are being fed large 
amounts and are growing the fastest. 
Table 7 shows that the period from 
day one through seven is when the 
percent of birds defecating becomes 
progressively higher each day. This 
is also the time when the greatest 
amount of tissue is being added to 
the total body weight. Holcomb and 
