This species has a small population numbering less than 10,000 mature individuals and is thought to be declining as a result of ongoing habitat degradation and possibly invasive species within the range. It is therefore classified as Vulnerable.

Eunymphicus cornutus is endemic to New Caledonia (to France). It is absent from the Isle of Pines (A. Legault in litt. 2016). It is mainly concentrated in the south of Grand Terre (Ekstrom et al. 2002).

The species is described as localised and uncommon or rare (Dutson 2011). During surveys in 2003-2006, the species was recorded on 57% of the massifs in the northern province, 42% of the massifs in the southern province, and was locally common in the central part of the main dividing range (Mé Maoya Massif, Moindou-Farino area, Poindimié-Ponérihouen area) (Chartendrault and Barré 2005, 2006, Legault et al. 2011). Its numbers were poorly known prior to 2006 (Chartendrault and Barré 2005, 2006) with only two independent population estimates of 1,000-3,000 birds (Ekstrom et al. 2000) and 720 pairs (N. Barré in litt. 1999), respectively. A more recent study using distance sampling density surveys, observation records, and ecological niche modelling indicates that its distribution extends over 3,482 km² and estimates that the population numbers 8,690 (7,934-9,445) birds (Legault et al. 2013b). This figure likely overestimates the population size due to the amount of forest cover used in this estimate, but the total population size is thought to number at least 5,000 mature individuals (V. Chartendault in litt. 2007). As such, it is here placed in the range 5,000-8,000 mature individuals.

The Horned Parakeet is patchily distributed in rainforest, and is occasionally seen in savanna, low-stature forest, and scrub (M. Thiollay in litt. 1999, Ekstrom et al. 2000, Ekstrom et al. 2002, Chartendrault and Barré 2005, 2006, Legault et al. 2011). The species generally prefers large, intact forests, particularly in valleys (Legault et al. 2011, 2012). It is typically found at intermediate altitudes (200-800m), though it has been observed at much higher elevations (Chartendrault and Barré 2005, 2006, Legault et al. 2011). It mainly feeds in the canopy, largely on seeds and nuts (Ekstrom et al. 2000, Legault et al. 2012). Nests are sometimes on the ground, including under rocks and in fallen tree-trunks (Hannecart and Létocart 1983, O. Robinet in litt. 1999, Dutson 2011), but it also nests in tree hollows (A. Legault in litt. 2016). It may migrate seasonally to foraging grounds during the austral winter from June to September (Chartendrault and Barré 2005, 2006). Birds have been seen crossing scrub between forest blocks, and it is not believed to be fragmented into distinct subpopulations (Y. Létocart in litt. 1999, Ekstrom et al. 2000). Birds are usually observed in pairs, or small groups (family members in April-June), with 90% of surveyed flocks containing fewer than 4 individuals (Legault et al. 2012), but larger flocks have occasionally been recorded (Ekstrom et al. 2000, V Chartendault in litt. 2007, Legault et al. 2012). The species is seen every year in the valleys, foraging in close proximity to rural dwellings and in open areas (V. Chartendault in litt. 2007). Nest sharing has been reported in this species (Theuerkauf et al. 2009).

Populations may be declining through habitat degradation, through logging, mining, fire and by introduced Rusa deer Rusa timorensis (Chartendrault and Barré 2005, 2006, Legault et al. 2012). Black rats occasionally prey on Horned Parakeet nests (Gula et al. 2010), but the magnitude of their impact remains to be quantified. Particularly wet (La Niña) years have been shown to reduce breeding success (J. Theuerkauf et al. in litt. 2011). There are no important local traditions that encourage the possession of pet birds ((N. Barré in litt. 1999, Ekstrom et al. 2000, Chartendrault and Barré 2005, 2006), and there is little documented evidence of trapping or trade, although birds are occasionally held in captivity on the island, and the species is sought by collectors (Pain et al. 2006). Poaching is unlikely to be a major threat, as the species breeds in remote areas, and its nests are hard to find. There is occasional illegal hunting (C. Meresse in litt. 2009). The introduction of Psittacine Beak and Feather Disease (PBFD) also poses a potential threat (Julian et al. 2012, Jackson et al. 2014).

There are no important local traditions that encourage the possession of pet birds ((N. Barré in litt. 1999, Ekstrom et al. 2000, Chartendrault and Barré 2005, 2006), and there is little documented evidence of trapping or trade, although birds are occasionally held in captivity on the island, and the species is sought by collectors (Ekstrom et al. 2002, Pain et al. 2006). Poaching is unlikely to be a major threat, as the species breeds in remote areas, and its nests are hard to find. There is occasional illegal hunting (C. Meresse in litt. 2009).

Conservation Actions Underway
CITES Appendix I and II, and fully protected by New Caledonian law. There are significant populations in Rivière Bleue, Parc des Grandes Fougères and Reserve Speciale de Faune et de Flore de la Nodela (Ekstrom et al. 2000, Legault et al. 2013 a, b). Since 2005 the Loro Parque Fundación has been supporting a long-term study on the species' ecology and threats (Theuerkauf and Rouys 2008). Captive-breeding populations are held in multiple locations (AviSoc; CITES prop. 11.33).

Conservation Actions Proposed
Survey other forest blocks within its extent of occurrence and investigate dispersal between isolated forest blocks (Ekstrom et al. 2000, Ekstrom et al. 2002). Investigate the breeding biology to identify any limiting factors such as nest failures or rat predation (Ekstrom et al. 2000, Ekstrom et al. 2002). Research ecological dependence on certain tree species for nesting or feeding (Ekstrom et al. 2000, Ekstrom et al. 2002). Continue to monitor numbers in Rivière Bleue and start a monitoring programme in Nodela (Ekstrom et al. 2000, J. Ekstrom in litt. 2003). Standardise the methods used to survey parakeet populations to facilitate comparison between different areas and time periods (Legault et al. 2013a). Monitor for any evidence of trapping and trade (Y. Létocart in litt. 1999, O. Robinet in litt. 1999, Ekstrom et al. 2000). Consider an Action Plan similar to that of E. uvaeensis (N. Barré in litt. 1999, Y. Létocart in litt. 1999, O. Robinet in litt. 1999, Ekstrom et al. 2000). Initiate control measures against introduced predators. Increase the area of suitable habitat that has protected status, with particular focus on conserving relatively intact rainforests on oligotrophic soils at intermediate altitudes (200–800 m), as these areas provide important parakeet habitat, yet are especially vulnerable to mining activities (Legault et al. 2011). Conduct a thorough evaluation of the IBAs described by Spaggiari et al. (2007) for their current and future potential as reserves (Legault et al. 2013b).