Behaviour There is no evidence of migration in this species, but it is prone to long-distance wandering in search of suitable habitat (Hancock and Kushlan 1984, Kushlan and Hancock 2005). It is usually seen alone, sometimes with other herons (Langrand 1990). It breeds mainly in small groups of a few pairs in mixed species colonies but also solitarily (Langrand 1990, del Hoyo et al. 1992, Koenig 2012, Safford and Hawkins 2013). Various independent observations suggest that nesting takes place year-round, although breeding success is likely to be low (Langrand 1990, ZICOMA 1999, Andrianarimisa et al. 2000). There are observations of Grey Heron Ardea cinerea and A. humbloti chicks occupying the same nests, leading to the possibility of mixed pairings or hybridisation, and this interaction between the two species is not understood (Andrianarimisa et al. 2000, Rabarisoa 2021). Habitat The species prefers coastal areas (including coral islets, mangroves, tidal mud flats and estuaries) (Hancock and Elliott 1978, Kushlan and Hancock 2005), but also frequents freshwater lakes (particularly those that persist through the dry season and are in close proximity to other lakes [Andrianarimisa et al. 2000]), rivers and, more rarely, rice-paddies (Hancock and Elliott 1978, Kushlan and Hancock 2005). It forages in clear, shallow waters (Hancock and Elliott 1978, Langrand 1990) and among floating vegetation (Hancock and Elliott 1978, del Hoyo et al. 1992). Habitat suitability depends on water clarity, shoreline areas with shallow water and the availability of large fish (Andrianarimisa et al. 2000). Diet It feeds chiefly on medium to large fish (up to 20 cm [del Hoyo et al. 1992]) and crustaceans (Langrand 1990, Morris and Hawkins 1998). Breeding Site It nests in tree-tops or hollows in rocks, and has also been reported to nest on the ground (Hancock and Kushlan 1984, Kushlan and Hancock 2005). Clutch size is three.

Ardea humbloti breeds almost exclusively in Madagascar, with one confirmed breeding record on Mayotte (to France), where it is also recorded as a regular visitor (Jeanne et al. 2015, eBird 2024). It is also a visitor to the Comoros Islands, although records are rarer and mainly pertain to Anjouan and Mohéli, with a possible breeding record on the latter (Safford and Hawkins 2013, Behrens 2021). It was previously considered fairly common (though patchily distributed) in parts of north and west Madagascar, with regular sightings from Lake Alaotra (ZICOMA 1999), and uncommon in the south (Langrand 1990). There were also occasional records in the central highlands and east of Madagascar (Safford and Hawkins 2013). However now the species is judged to be mainly restricted to western Madagascar, with the highest concentration in the western coastal area, but it is also widespread in the central parts of the country where suitable habitats exist. It gradually becomes scarcer as one moves south, and is practically absent from the eastern side of the mountains to the eastern coast, with very few recent records from this area (Andrianarimisa et al. 2000, REBIOMA 2016, Rabarisoa 2021, eBird 2024). It is also found offshore in the Anorontany archipelago (Rahaerilalao 2010).

Conservation Actions Underway
This species is recorded from Ankarafantsika Strict Reserve, Ankarana Special Reserve and Baly Bay National Park, but overall its habitat is poorly protected (Langrand 1990), with c.50% of the population residing outside protected areas (Andrianarimisa et al. 2000). The Malagasy government has ratified the Ramsar Convention, which came into force for the country in 1999, and this may herald improved conservation measures for wetlands. During surveys in the Antsalova region in 2003/2004, the numbers of this species, on average for each site, were found to be significantly higher on lakes in designated Ramsar Sites (lakes Befotaka, Soamalipo, Ankerika and Antsamaka) compared with lakes outsite designated sites (Andrianarimisa et al. 2000). However, this could be due to variations in survey effort, the availability of suitable shoreline habitat, the proximity of the relatively undisturbed Tsimembo Forest, which prevents serious soil erosion, or the proximity of lakes to one another (Andrianarimisa et al. 2000). A survey in 1999 found the species in 20 Important Bird Areas within the West Malagasy Endemic Bird Area (ZICOMA 1999).

Conservation Actions Proposed
Develop a national action plan for the species (Rabarisoa 2021). Locate and protect important breeding colonies. Reinforce the protection of protected areas, and increase the amount of conservation activities within protected areas (Rabarisoa 2021). Continue monitoring to maintain up-to-date population size and trend estimates for the species. Improve knowledge of the species' ecology (Rabarisoa 2021). Create community conservation groups to improve conservation of the species outside of protected areas (Rabarisoa 2021). Raise awareness about the species and its threats (Rabarisoa 2021).