Reproductive status of a female white cockatoo (Cacatua alba) based on relationships among urofecal steroid hormone dynamics, molting, and body weight

**Background:** The reproductive physiology of cockatoos, particularly regarding gonadal hormone dynamics, is poorly understood. Noninvasive monitoring of sex steroid hormones in urofeces offers a stress-free alternative to blood sampling, especially for rare or endangered species. This study aimed to characterize ovarian activity in a female white cockatoo (*Cacatua alba*) by measuring urofecal estradiol-17β (E2) and progesterone (P4) and relating these to egg-laying dates, body mass changes, and molting patterns.

**Methods:** One captive female white cockatoo (at least 20 years old) that regularly laid unfertilized eggs was studied. Urofeces were collected twice weekly from July 2016 to June 2017 and April 2018 to July 2021 (total ~4 years). E2 and P4 concentrations were measured by enzyme immunoassay (detection limits: 6.4 pg/mL for E2, 5.0 pg/mL for P4; intra-assay CV: 8.4% for E2, 5.8% for P4; inter-assay CV: 12.7% for E2, 13.4% for P4). Body mass was recorded from April 2018 to July 2021. Fallen feathers were collected from December 2018 to October 2020 and categorized by type and size. Hormone baselines were calculated using an iterative process (mean + 2 SD). The egg-laying period was defined as the time when one or two eggs were laid. Data were analyzed using one-way ANOVA with Dunnett's post-hoc test (for hormone concentrations and body weight) and Kruskal-Wallis with Steel's test (for feather counts).

**Key Results:** Over the study period, there were 22 egg-laying periods, with an average clutch size of 1.8 eggs (range: 1–2). The average interval between eggs within a clutch was 4.5 ± 1.1 days (range: 3–8 days), and the average interval between egg-laying periods was 52.1 ± 10.8 days (range: 40–76 days). Urofecal E2 concentration began to increase an average of 18.6 ± 2.4 days before the first egg was laid. Urofecal P4 concentration peaked an average of 17.7 ± 3.1 days after the start of the E2 rise, and the first egg was laid an average of 0.9 ± 2.5 days after the P4 peak. The peak E2 concentration occurred an average of 5.8 ± 4.3 days before the P4 peak. Body weight averaged 429.3 ± 14.0 g (range: 398.0–506.5 g) and showed a significant positive correlation with urofecal E2 dynamics (r=0.503, n=338, P<0.0001). Body weight increased by an average of 26.8 g (6.2% of mean annual body weight) before egg laying and decreased by an average of 19.7 ± 5.9 g after the first egg (7.8% of pre-laying weight). When two eggs were laid, the total weight loss from before the first egg to after the second egg averaged 38.4 ± 7.9 g. Molting, assessed by the number of fallen feathers, decreased in 10 out of 11 egg-laying periods after the start of the E2 increase, and increased after E2 returned to baseline.

**Clinical Implications:** This study demonstrates that noninvasive urofecal hormone monitoring can accurately capture ovarian activity in white cockatoos, with E2 reflecting follicle growth and P4 indicating ovulation. Body weight changes can serve as a practical predictor of follicular development. The antagonistic relationship between reproduction and molt suggests that molting is suppressed during periods of high ovarian activity. These findings provide a foundation for improving captive breeding programs and health monitoring in this endangered species. Limitations include the use of a single individual and twice-weekly sampling, which may have missed some P4 peaks. Future studies with more frequent sampling and additional females are needed to confirm these patterns.