Question

osprey ecosystem
ospreys are predatory birds that typically nest in open, high places. scientists
monitor the open nests of a native osprey population in an estuary habitat affected
by human activities. the scientists observe the naturally occurring feeding
relationships in the osprey ecosystem, as shown in the table.
ospreyecosystem
feeding relationships
menhaden(small
fish) phytoplankton,
zooplankton
striped bass menhaden, herring
osprey menhaden, striped
bass
raccoon young osprey, eggs,
frogs, nuts
the scientists noted the following events affecting the ecosystem:

• striped bass harvest increased with an increase in local commercial fisheries.
• due to overfishing, restrictions on striped bass harvest were enforced to reduce

effects on the population.

• a conservation project restoring eagle populations from a similar ecosystem has

introduced eagles into this osprey ecosystem.

• eagles fill the same niche as ospreys.

the graph shows how these events within the ecosystem have affected the osprey
population over time.
which statement describes a possible effect of the introduction of the eagle
into the osprey ecosystem?
a osprey mating calls will change in tone and frequency.
b osprey migrations will become shorter and less frequent.
c osprey will produce fewer eggs in each breeding season.
d osprey will become more selective for fish during hunts.

Explanation:

When eagles are introduced and fill the same niche as ospreys, they compete for resources. This competition can lead to reduced availability of resources for ospreys. One of the effects of resource limitation (due to competition) in many species is a decrease in reproductive output. Fewer eggs per breeding season is a possible outcome as the ospreys may have less energy to invest in reproduction due to increased competition for food (since they share the niche, food resources like fish - as seen in the feeding relationships where ospreys eat striped bass and menhaden - may be more limited).

• Option A: There is no indication in the given information (about feeding relationships, competition due to niche overlap) that would suggest a change in mating call tone and frequency. Mating calls are more related to species - specific communication and not directly to competition for resources in this context.
• Option B: Migrations are often related to seasonal changes in food availability (e.g., moving to warmer areas with more food in winter) or breeding grounds. The introduction of eagles (competing for the same local resources) does not imply a change in migration patterns (shorter and less frequent) as described.
• Option D: If anything, with more competition for food (since eagles are in the same niche), ospreys might have less ability to be selective (they would take whatever fish is available) rather than becoming more selective.

Answer:

C. Osprey will produce fewer eggs in each breeding season.