Aspectos reprodutivos de uma população de guará (Eudocimus ruber) sob cuidados humanos em baixa latitude.

Abstract

This thesis was divided into two chapters. In the first chapter, the objective was to describe the embryonic development of semi-altricial scarlet ibis (Eudocimus ruber) while identifying critical landmarks for diagnostic and age determination purposes, supporting both artificial incubation and field research on the species. We used eggs collected from a captive population in northern Brazil. A total of 50 embryos were analyzed from day 0 to day 18, focusing on external morphological traits observable through macroscopic examination. Key diagnostic features included the sequential formation of the beak, eyes, neck, feathers, and embryonic annexes. We compared the development of the semi-altricial scarlet ibis with reference descriptions of precocial and altricial species to evaluate the suitability of comparisons between different postnatal growth patterns. The semi-altricial scarlet ibis exhibited heterochronic variations of up to four days in critical developmental landmarks compared to precocial species with similar incubation periods. These findings suggest that developmental timelines. established for precocial species may not be reliable for accurately staging altricial and semi-altricial embryos. Interestingly, the median timing of significant developmental events in the scarlet ibis aligned more closely with those of other altricial species. The daily embryonic milestones described herein provide a valuable reference for scarlet ibis captive breeding programs and contribute to broader conservation efforts for other Threskiornithidae family members or species within the Pelecaniformes order, addressing the limited research on semi-altricial avian development. In the second chapter, we aimed to describe the breeding performance of a captive population of scarlet ibis over a three-year period (2022, 2023, and 2024). We focused on various factors, including the onset and conclusion of the breeding season, couple formation, enclosure density, and laying timing. We conducted statistical analyses to assess the impact of breeder-related factors (such as age and laying timing), egg characteristics (including weight and shape), and incubation parameters (such as egg weight loss) on key zootechnical variables commonly used in poultry production, including laying rate, fertility, and hatchability. Our goal was to establish a breeder profile that could inform mate selection. The onset of the breeding season varied between July and August over the three years, while its conclusion ranged from November to January. Both males and females began forming breeding pairs as early as two years old, with the oldest pairing ages being 20 years for males and 12 years for females. 82,6 ± 4.9% of pairs were monogamous throughout the season. Higher enclosure densities appeared to improve laying rates and encourage earlier laying, while a 1:1 male-to-female ratio facilitated effective pair formation with minimal aggression. Additionally, increased female age correlated with a higher laying rate (p < 0.05). Egg withdrawal stimulated the replacement of eggs in females, resulting in an average of 7.6 ± 2.7 new eggs. The advancement of the laying season significantly influenced initial egg weight (p < 0.01). The median daily weight loss during incubation was 0.74% (tau = 0.5), while the mean weight loss on day 21 was 19 ± 2%. The findings from this study are invaluable for planning efficient breeding programs for the scarlet ibis and potentially for other members of the Threskiornithidae family.