Foraging behavior and daily activity periods
Lilac-crowned Parrots forage in the canopy, and can form large feeding flocks in fruiting trees. In tropical dry forest of coastal Jalisco, most foraging activity of parrots is conducted during the first 3 hours of the morning and last 2-3 hours of the afternoon (Salinas-Melgoza and Renton 2005). Peak movement of individuals occurs in the early morning from 06:30 to 09:30, and late afternoon from 18:30 to 19:30, when parrots fly to and from communal roost-sites and foraging areas (Salinas-Melgoza and Renton 2005). Lilac-crowned Parrots are generally inactive and do not move location for 5–6 hr from 11:00 to 16:00 hrs (Salinas-Melgoza and Renton 2005). During this period, parrots take refuge from the heat of midday beneath the shade of foliage, or take advantage of warm breezes at the top of exposed ridges.
Information on nesting behavior is obtained from observations conducted on nesting Lilac-crowned Parrots in coastal Jalisco, and reported by Renton and Salinas-Melgoza (1999).
Lilac-crowned Parrots commence egg-laying and incubation in early February. The incubation period lasts 28-29 days (Mann and Mann 1978), during which the female remains in the nest throughout the day, leaving the nest only twice a day in the morning and late afternoon to be fed by the male. Conversely, the male rarely enters the nest, apart from at the time of initial egg-laying. Food transfer from the male to the female usually takes place away from the nest cavity, and is the only time during the incubation phase when both adults are away from the nest area for an average 11.5 mins each food transfer session.
Following hatching of the eggs, females continue to brood nestlings throughout the day during the first three weeks. During this early nestling phase, the male feeds the female twice a day, and may occasionally enter the nest. Later in the nesting cycle when the chicks are larger the female leaves the nest during the day to forage with the male. At this time, both parents enter the nest to feed the young twice a day, and are extremely secretive and cautious when approaching the nest.
Prior to fledging, nestlings climb to the nest entrance, and may be fed at the nest rim. At this stage, nesting pairs spend more time perched near to the nest entrance making low contact vocalizations to the young to encourage fledging. Most young fledge from the nest by mid to late May.
The Lilac-crowned Parrot forms communal roosts of hundreds of birds. Schaldach (1963) reported roosts of two to three hundred birds in Colima, while Stager (1954) reported several hundred parrots flying in just before dark to roost in a stand of oaks at 1,400 m in Barranca de Cobre, Chihuahua. Lilac-crowned Parrots gather in large flocks during the final hour of the day, and roost in the branches of trees at the top of ridges or near the summit of the tallest hills. Parrots leave the roost-site at first light in the morning. A number of roost-sites may be used by parrots on any one night, and individuals may change their use of a roost location after a few days (K. Renton unpubl. data).
Lilac-crowned Parrots do not defend a feeding territory and tend to form sociable feeding flocks. However when breeding, the nesting pair will defend an area around the nest cavity prohibiting access to the area by other potential nesting pairs. This defense takes the form of vocal duets by the nesting pair, occasional visual displays by raising the wings when another pair is in sight, and moving towards other individuals to chase them from the area when they approach near to the nest cavity (K. Renton pers. obs.). The spacing requirement of nesting pairs may limit breeding densities, with a separation distance of an average 1 km between active parrot nests (Salinas-Melgoza et al. 2009).
The Lilac-crowned Parrot is a monogamous species, maintaining pair formation throughout the year. Mating occurs during February and early March prior to egg-laying, and the pair no longer mate once the female has laid all the eggs in the clutch (K. Renton pers. obs.).
Social and interspecific behavior
The main social unit for Lilac-crowned Parrots is the mated pair, particularly during the breeding season. Pair bonds are relatively permanent, however if one of the mated pair should be lost due to predation, it is likely that the remaining individual will find a new mate. On one occasion, after the loss of an incubating female from predation, the male of the pair was observed to return to the nest-site each day calling for the female, though she never reappeared. By three weeks after the predation event, the male still returned each day to the nest-site to call for the predated female, however he was now followed by another individual, and even appeared to feed that individual (K. Renton pers. obs.). Hence, it is likely that a new pair bond would be formed.
Parrots may form large flocks in feeding trees or roost-sites, but will usually break-up into pairs or small family groups when leaving the site of aggregation. After fledging from the nest the pair do not divide-up care of the young, but keep the family group together, both parents feeding each fledgling in turn (K. Renton pers. obs.).
Radio-telemetry studies have shown that young birds remain in the family group for at least 5 months after fledging (Salinas-Melgoza and Renton 2007). Hence, during the months of June to October small groups of 3, 4, and 5 parrots probably represent family groups of a mated pair with associate young. After break-up of the family group, siblings usually travel in opposite directions and move in separate flocks (K. Renton unpubl. data). At this stage, radio-marked juveniles from different family groups have been found together, but separate from their siblings, indicating that recently independent young may aggregate in nomadic juvenile flocks (K. Renton unpubl. data). After reaching independence from the family group, some juveniles disperse from the natal area.
Most predation occurs on eggs and nestlings while in the nest. The main predators of Lilac-crowned Parrot nests are reptiles such as the Boa Constrictor, Indigo Snake (Drymarchon corais) and the Black Iguana (Ctenosaura similis), as well as mammals such as the Virginia Opossum (Didelphis virginiana) and White-nosed Coati (Nasua narica). Incubating females are also vulnerable to predation while in the nest cavity, and have been found predated by White-nosed Coatis or killed by Africanized bees when they take over the nest cavity (K. Renton pers. obs.). The Crane Hawk (Geranospiza caerulescens) is another predator of Lilac-crowned Parrot nestlings, frequently being observed using its long, double-jointed legs (Howell and Webb 1995) to reach inside shallow nest cavities and extract the contents (K. Renton pers. obs.). After leaving the nest, Lilac-crowned Parrot fledglings have a 73% probability of survival, with all mortalities occurring within the first 5 weeks after fledging (Salinas-Melgoza and Renton 2007). The main predators of juvenile and adult parrots are hawks such as the Grey Hawk (Buteo nitidus) and Collared Forest Falcon (Micrastur semitorquatus), both of which have been observed attempting attacks on adult Lilac-crowned Parrots (K. Renton pers. obs.).