Six different kinds of blackbirds were studied in Mississippi and California to see how they responded to change in their environment. Resident blackbirds were more tolerant of change than migratory blackbirds.
A constantly changing environment, whether caused by humans or nature, is a fact of life for the modern avian world. How different kinds of birds react to that change may impact their long-term survival.
Resident blackbirds, such as grackles, cowbirds, and red-wings and Brewer's in California; were compared to migratory species, such as rusty and tricolored blackbirds, and Brewer's in Mississippi to see how they reacted to change in their environment.
To test the birds' fear response, seed was placed on the ground in a variety of habitats. Then, objects, plastic windmills for example, were placed around the seed to see if this caused the birds to hesitate before feeding.
Below are two video clips showing the experiments in action.
The first shows a control experiment—one where there are no objects.
A pile of bird food has been placed on the ground.
Initially, the blackbirds are hesitant but they approach the food fairly quickly and once the first birds begin eating, there is a mad rush of birds to devour the remaining food.
In the second video clip, blue plastic windmills have been placed to surround the food.
The birds take much longer to feed although they are quite aware of the food. They are reluctant to pass by the objects to get to it and spend less time feeding.
Although all blackbird species were more hesitant to feed when confronted with something unfamiliar around their feeding area, the results were much more profound for migratory birds.
The birds must weigh the costs of feeding in unfamiliar surroundings, predation or injury, against the temptation to feed. For resident birds, the cost appears to be less. They may be tempted to feed earlier than others because they are confined to the area year-round whereas migrants can always leave. For migrants, the risks of predation and injury may make them more fearful.
The inability to adapt to a rapidly-changing world may have consequences for migratory birds. Perhaps not surprisingly, the most migratory of the blackbirds studied, the rusty blackbird, is the most declining songbird in North America, and is the most fearful of novelty.
This article summarizes the information in this publication:
Mettke-Hofmann C, Winkler H, Hamel PB, Greenberg R (2013) Migratory New World Blackbirds (Icterids) Are More Neophobic than Closely Related Resident Icterids. PLoS ONE 8(2): e57565. doi:10.1371/journal.pone.0057565
Environments undergo short-term and long-term changes due to natural or human-induced events. Animals differ in their ability to cope with such changes which can be related to their ecology. Changes in the environment often elicit avoidance reactions (neophobia) which protect animals from dangerous situations but can also inhibit exploration and familiarization with novel situations and thus, learning about new resources. Studies investigating the relationship between a species’ ecology and its neophobia have so far been restricted to comparing only a few species and mainly in captivity. The current study investigated neophobia reactions to experimentally-induced changes in the natural environment of six closely-related blackbird species (Icteridae), including two species represented by two distinct populations. For analyses, neophobic reactions (difference in number of birds feeding and time spent feeding with and without novel objects) were related to several measures of ecological plasticity and the migratory strategy (resident or migratory) of the population. Phylogenetic relationships were incorporated into the analysis. The degree of neophobia was related to migratory strategy with migrants expressing much higher neophobia (fewer birds feeding and for a shorter time with objects present) than residents. Furthermore, neophobia showed a relationship to diet breadth with fewer individuals of diet generalists than specialists returning when objects were present supporting the dangerous niche hypothesis. Residents may have evolved lower neophobia as costs of missing out on opportunities may be higher for residents than migrants as the former are restricted to a smaller area. Lower neophobia allows them approaching changes in the environment (e.g. novel objects) quickly, thereby securing access to resources. Additionally, residents have a greater familiarity with similar situations in the area than migrants and the latter may, therefore, initially stay behind resident species.
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