Question

By treating house martins (Delichon urbica) with antimalarial drugs, Marzal et al. (2005) were able to show that the malarial blood parasites in Spain reduced production of young birds by about \(40 \%\) In Denmark house martins do not carry this malarial parasite. Would you expect the population density of these birds to be higher in Denmark? Why or why not?

Short answer

The population density of house martins in Denmark is likely higher due to the absence of the malarial parasite, assuming other conditions are similar to those in Spain.

Step-by-step solution

Understand the Role of Malarial Parasites

In Spain, house martins experience a reduction in the production of young birds by around 40% due to malarial parasites. This implies that these parasites have a significant negative impact on the reproduction rate of the population.

Examine the Situation in Denmark

Compare the situation in Denmark, where house martins do not carry the malarial parasite. Without the parasite, they might not experience the same reduction in reproductive success, suggesting they could potentially produce more offspring in comparison to their Spanish counterparts.

Consider Population Density Factors

While the absence of the malarial parasite suggests higher reproduction rates, other factors also affect population density. These factors include food availability, nesting sites, and environmental conditions, which may vary between Spain and Denmark.

Conclusion on Population Density

If other factors are similar, the absence of the malarial parasite in Denmark should lead to a higher population density due to increased reproductive success. However, if Denmark has less favorable conditions for other factors, it could neutralize the reproductive advantage.

Key concepts

Malarial Parasites

Malarial parasites can have a profound impact on wildlife populations. They are microorganisms that live inside the blood of animals, including birds such as house martins in Spain. These parasites cause diseases that can severely affect the health and reproduction of their hosts. In Spain, for example, these malarial parasites reduce the reproduction rate of house martins by about 40%. This significant drop affects not only the health of individual birds but also the sustainability of the entire population.
A reduced reproduction rate leads to fewer new birds being born, which can eventually lower the population density. This is because with fewer offspring, the overall number of birds decreases over time. In regions where the parasite is prevalent, such as Spain, managing and controlling these parasites can be crucial for conserving bird populations.
Treating birds with antimalarial drugs, as done by Marzal et al., was one way to mitigate these effects and help in maintaining bird populations by improving their reproduction rates.

Reproduction Rate

The reproduction rate is a critical metric used to understand population growth or decline. In simpler terms, it tells us how many offspring an organism or a group can produce in a certain period. House martins in Spain are negatively affected by malarial parasites, which dramatically lowers their reproduction rate.
If a population has a lower reproduction rate, it means fewer individuals are added to the population over time, potentially leading to a decline in population density. In contrast, a higher reproduction rate often indicates a growing population.
In Denmark, house martins do not carry the malarial parasite that affects their reproduction. Without this burden, they have the potential to produce more offspring, assuming all other conditions remain favorable. This could lead to a stable or even increasing population density.

• High reproduction rate: More offspring, potential increase in population.
• Low reproduction rate: Fewer offspring, potential decrease in population.

Environmental Conditions

Environmental conditions are the external factors that influence where and how a species thrives. For house martins, this includes food availability, nesting sites, and climate aspects such as temperature and humidity. These factors are just as crucial as the absence of diseases like malaria. In Denmark, even though house martins are free from the malarial parasite, their population density also depends on these environmental conditions.
For instance, if Denmark offers abundant food and suitable nesting sites, it provides an optimal environment for house martins to reproduce and grow their population. However, less favorable conditions, such as scarce food resources or unsuitable climate, could negate the reproductive advantages gained by the absence of parasites. This highlights the need to look at the whole picture when evaluating population densities.

• Food availability: Essential for survival and reproduction.
• Nesting sites: Critical for breeding success.
• Climate: Can impact overall health and survival.

Even without a parasitic burden, poor environmental conditions can prevent a population from growing, underscoring the complex interplay of factors affecting population density.