Crested Wood Partridge (Rollulus rouloul)
Hatchability Study
Introduction:
For the project requirement of the internship, an egg log data file for the crested wood partridge (Rollulus rouloul) was created using Microsoft Excel. Once this was completed, a factor in regards to hatchability was selected and an analysis was performed.
Species Information:
The crested wood partridge (CWP) belongs to the Pheasant family (Phasianidae) and is about ten inches in length. The male and female are similar in size but dimorphic in appearance. The male has a dark bluish body with a red crest, whereas the female has a greenish body with brown wings. and no crest. Both sexes have an exposed fleshy eye ring which is bright red in color.
Their distribution is found in the SE Asian countries of S. Burma, S. Thailand, Malaya, Sumatra, and Boreo. They may be found in lowland and hill evergreen dipterocarp forests, up to 4000 feet. Their diet consists of fruit, seeds, insects, and plant stems. Their social structure consists of pairs or small parties from one to thirteen birds.
The domed nest consists of dead leaves and stems and has a side entrance. The clutch size ranges from 4 to 6 white eggs which are incubated by the female for 18-19 days. Both the male and the female feed the brood for 5-6 days and the young will stay with the parents for about three months (Source: J. Pichner, MN Zoo Avian Zoologist).
Compilation and Creation of Species Data File:
Prior to the analysis, an incomplete data file for the crested wood partridge was referenced and randomly checked against the actual written egg log . However there were some major discrepancies found and as a result all entries were checked and then corrections and/or additions were made. In addition to the written egg logs, species record sheets and taxon reports were referred to for additional eggs (esp. those which were parent-reared as opposed to hand-reared) and these were added to the data file. The information in the data file included the:
egg number (assigned to those eggs incubated. "N/A" for those which were parent-reared);
incubation type (1= hand-reared, 2= parent-reared);
I.D./accession number (given to those which successfully hatched);
sire;
dam;
date laid (if given);
hatch date;
death date;
days lived;
egg status;
egg code (1= infertile, 2= early dead, 3= late dead, 4= hatch);
length of egg (mm);
width (mm)
weight (g);
and any relevant comments.
Once completed, the data file consisted of 21 years (1978-1998) of crested wood partridge egg data. There was a grand total of 1006 entries.
Generation of Possible Analyses:
After the completion of the data file, a factor was selected to see what kind of correlation could be made in regards to hatchability. Factors such as egg dimensions, sire, dam, and incubation type, can be analyzed to identify trends in the egg code and then these findings can be used or manipulated to improve the hatchability of a species.
For this analysis, the effects of a change in management practice for hand-reared eggs was performed to identify trends in hopes of improving hatchability.
Background on Weight Loss Management of Hand-Reared Eggs:
The oxidation of fat in the yolk sac produces waste products of carbon dioxide and metabolic water which diffuse from the egg shell as the embryo develops. As a result of this diffusion, the egg loses weight as it develops. However the rate at which this occurs can affect the survivability of the embryo since rapid water loss can result in dehydration and slow water loss can result in the drowning of the embryo (Source: Mark Bergland, UW-RF 1999 Ornithology Study Guide, p. 50).
Before 1988, the Minnesota Zoo ran a linear daily weight loss for crested wood partridge eggs with the end result being a 15% weight loss. However after comparing the weight losses for hatched and unhatched eggs, it was found that eggs which had a 17% weight loss were more successful at hatching. It was also found that amongst the 17% group, a non-linear weight loss in which eggs had an 11% loss for the first half of incubation and then 20% loss for the last half were much more successful. For the total incubation, the final weight loss for this non-linear method was still 17%.
This non-linear, 17% weight loss method was found to have a hatch success rate of 98% and was thus implemented after 1988 (Source: J. Pichner).
Results:
A table was generated to compare the hand-reared egg codes both before and after the the change in daily weight loss management:
| Early dead | Late dead | Hatch | Total | |
| pre- 1988 | 13.94 % | 48.56 % | 37.50 % | 100.00 % |
| post- 1988 | 14.07 % | 17.04 % | 68.89 % | 100.00 % |
A chi-square test was used to compare pre- and post- egg code percentages for each of the three groups. As expected just from viewing the table above, there was no significant difference for the "early dead" group (chi-square = 0; p = 1). However, significant differences did exist for the "late dead" group (chi-square = 15.5152; p = < 0.0001), and the "hatch" group (chi-square = 8.9813; p = 0.0027).
Conclusion:
The 1988 change in the daily weight loss method had a significant impact on the hatchability of crested wood partridge eggs. The Minnesota Zoo's bird crew knew this however it was never proven statistically. Before 1988, the majority of eggs were late dead (48.56%). After 1988, the majority were hatchers (68.89%). Studies such as this, illustrate the importance of analyzing past management techniques in order to identify trends and implement new strategies. The identification and manipulation of trends in incubation methods and its effects on hatchability rates are extremely important in zoological facilities. This information can be applied not only to maintaining animal collections but to threatened and endangered species recovery.
