Eggs were incubated in the laboratory at more nearly optimum
temperature and humidity than were eggs in natural nests. Percentage
of prenatal mortality probably was lower in laboratory-incubated eggs
than in those under natural conditions.
Of sixty eggs studied in the laboratory, 45 (75 per cent) were
fertile; 36 (80 per cent) of the fertile eggs (those in which the
blastodisc was at some time discernible by transmitted light) hatched
successfully. In six clutches all the eggs were fertile and five of
these clutches hatched with 100 per cent success. One clutch contained
eggs that were all infertile and another clutch had four infertile
eggs and two fertile eggs that failed to hatch. Among nine fertile
eggs that failed to survive, four casualties occurred in the late
stages of incubation or after hatching had begun, indicating that
these are probably critical periods.
Fertility of eggs was not correlated with size or age of female, with
size of clutch, or with size of egg. Eggs laid in the laboratory had
higher rates of infertility and prenatal mortality than did eggs
dissected from oviducts. Handling of eggs in removing them from nests
to incubation dishes, after embryonic development had begun, might
have been responsible for reduced viability (Table 2).
TABLE 2.--Comparative Rates of Fertility and Prenatal Mortality for
Eggs Dissected from Oviducts and for Eggs That Were Laid in the
Laboratory and Subsequently Removed to Incubation Dishes.
===========================+==============+===============
| Eggs removed | Eggs dissected
NUMBER OR PERCENTAGE | from nests | from oviducts
---------------------------+--------------+---------------
Number of eggs examined | 22 | 38
---------------------------+--------------+---------------
Percentage of fertile eggs | 64 | 82
---------------------------+--------------+---------------
Percentage of fertile | |
eggs hatched | 50 | 94
---------------------------+--------------+---------------
Percentage of eggs hatched | 32 | 76
---------------------------+--------------+---------------