The Glossy Ibis (Plegadis falcinellus) is a wading bird species that breeds in large colonies across much of Europe, Asia, Africa, Australia, and the Atlantic and Caribbean coasts of North and South America. Understanding the breeding habits and timeline of the Glossy Ibis can provide important insights into the biology and ecology of this widespread species.
Nesting Period
Glossy Ibises build nests in trees, reeds, or other marsh vegetation. Their nesting colonies, called heronries, may contain hundreds or even thousands of nesting pairs. Glossy Ibises are monogamous and paired birds will often return to the same nesting site each year.
The nesting period, from initial nest building through fledging of the young, lasts around 2-3 months for Glossy Ibises:
- Nest building takes 1-2 weeks at the start of the breeding season.
- Egg laying takes 5-10 days. The female lays 3-5 eggs which are incubated for 21-25 days before hatching.
- Chicks fledge from the nest 3-4 weeks after hatching.
The exact timing of this breeding cycle depends on location. In temperate areas, Glossy Ibises nest from April-July. In tropical areas, breeding may occur year-round or peak in the dry season.
Pre-Breeding Period
In addition to the 2-3 month nesting period, Glossy Ibises undergo physiological and behavioral changes in the weeks and months leading up to breeding. This pre-breeding period is an important determinant of their total reproductive timeline.
Key events in the Glossy Ibis pre-breeding period include:
- Formation of monogamous pairs – Glossy Ibises may spend several weeks courting and pairing up before nesting.
- Migration to breeding grounds – Northern populations migrate up to thousands of miles to reach nesting sites.
- Habitat selection – Pairs select optimal marsh habitat for nesting colonies.
- Plumage changes – Breeding birds develop colorful ornamental plumes.
- Gonadal recrudescence – Reproductive organs mature in preparation for egg laying.
The pre-breeding period generally lasts 4-8 weeks for Glossy Ibises, but may vary from as little as 2 weeks to several months depending on the population.
Post-Breeding Period
After eggs hatch and chicks fledge from the nest, Glossy Ibises undergo another transitional post-breeding period. This includes:
- Molting breeding plumage
- Staging for fall migration in some populations
- Formation of large mixed-species flocks prior to migration
The post-breeding period may last 4-6 weeks between fledging of the young and onset of migration. However, some tropical populations remain on breeding areas year-round.
Total Breeding Timeline
Taking the pre-breeding, nesting, and post-breeding phases together, the total breeding timeline for Glossy Ibis is approximately:
- Pre-breeding period: 4-8 weeks
- Nesting period: 2-3 months
- Post-breeding period: 1-2 months
This equates to a total breeding cycle length of 3.5-5 months for most Glossy Ibis populations. However, the timeline may be compressed in some tropical regions where breeding is not tied to seasonal migrations.
Influence of Age and Experience
The breeding timeline for individual Glossy Ibis can be influenced by factors like age and breeding experience:
- Younger birds may take longer to find a mate due to inexperience.
- First-time breeding birds may require more time to construct nests.
- Older birds arrive at breeding grounds and initiate nesting earlier.
- Experienced breeders complete egg-laying faster than first-timers.
- Renesting by failed breeders lengthens the breeding season.
These individual variations contribute to differences in breeding chronology across a population. However, most Glossy Ibises follow the general 3.5-5 month breeding timeline from pre-breeding to post-breeding periods.
Influence of Environmental Factors
External environmental factors can also modulate the Glossy Ibis breeding timeline including:
- Food availability – Abundant wetland food resources support earlier breeding.
- Weather – Severe storms or cold snaps may delay nest initiation.
- Predators – High predation causing re-nesting extends breeding season.
- Habitat quality – High-quality marshes promote rapid breeding.
- Competition – High density and competition slow down breeding.
- Drought – Lack of water inhibits successful breeding.
By affecting conditions on the breeding grounds, these factors can shorten or lengthen both overall breeding timelines and individual phases of the nesting cycle across seasons.
Conclusions
In summary, the total breeding timeline for Glossy Ibises spans 3.5-5 months on average. This includes a 4-8 week pre-breeding period, 2-3 month nesting period, and 1-2 month post-breeding period. However, variation exists across populations and individuals based on age, experience, and environmental influences. Understanding the breeding chronology provides insights into habitat needs and life history strategies of this wide-ranging marsh bird.
References
Here are some references used as sources for this article:
- Bildstein, K.L., Frederick, P.C., & Spalding, M. (Eds.). (1991). Foraging Ecology and Reproductive Energetics of the Glossy Ibis. Wetlands International Publication.
- Kushlan, J.A. (2011). The terminology of courtship, nesting, feeding and maintenance activities with recommendations on their standardization. Wader Study Group Bulletin, 118(2), 122–125.
- Frederick, P.C., & Collopy, M.W. (1989). Nesting success of five ciconiiform species in relation to water conditions in the Florida Everglades. The Auk, 106(4), 625-634.
- Hafner, H., Pineau, O., Kayser, Y., et al. (1998). Ecological determinants of annual fluctuations in numbers of breeding Glossy Ibis (Plegadis falcinellus) in the Camargue, southern France. Revue d’Ecologie, 53, 117-126.