UÉ studies the use and effects of aromatic plants in Blue Tit nests

foto: Luísa Sequeira

Some species of birds add aromatic plants in the construction of nests, such as the Common Starling (Sturnus vulgaris), the Black Starling (Sturnus unicolor) or the Bonelli's Eagle (Hieraaetus fasciatus). The PhD thesis in Biology by Bárbara Pires, allowed us to advance with several hypotheses related to the concealment / shade of the nests, among them the regulation of water loss and heat levels, allowing to considerably improve the knowledge on this theme, introducing new study variables , new methodologies and new ideas.

To explain this behavior, Bárbara Pires argues that “in secondary cave birds, as is the case with Blue Tit, the hypotheses related to the reduction of parasite populations and the improvement of the condition of the young have been valued to explain this behavior”, noting that the nests are often reused year after year, so the chicks "are more exposed to parasites, mainly due to the fact that several species of insects hibernate in the cavities during the winter" he highlights.

In this way, and evaluating by his study, “the young birds of cave birds are affected by parasites that are present in the nests through direct contact, but also through the body condition of the parents” emphasizes Bárbara Pires, adding that the parents and chicks " adopt different defense mechanisms to limit and / or alleviate the harmful effects of these parasites ".

The cavities where the nests are built, as he suggests, "provide protection from predators and more unfavorable environmental conditions, so they provide an excellent shelter for the young, but also for insects that use the cavities to reproduce and feed" stresses Bárbara Pires , mentioning that these insects are parasites of birds, feeding on skin, feathers and blood.

In this case, "they can parasitize both the offspring and the parents, but in the process of these parasites feeding on birds, they can transmit blood parasites that, although it is not confirmed that they cause the death of both offspring and parents, weaken the organism a lot" he also mentions, stressing that the condition of the parents "will have a direct effect on the condition of the offspring: if the parents are in poor body condition or parasitized, the care they provide to the offspring will be compromised".

Bárbara Pires, thus indicates that the incorporation of specific aromatic plants in blue-throated nests allowed “produced offspring with a larger tarsus, but only in large litters”, verifying that, even with aromatic plants supplementation in the nests, the females of Blue Tit “added plants chosen by you, with a very different usage pattern, and not always directly related to the availability of these plants in the area surrounding the nests”.

In addition to these observations, "significant relationships between aromatic plants added to the nests by the females, weight of the nests, laying date and reproductive parameters" were also verified, results provide new perspectives on how the females of Blue Tit "use aromatic plants in their nests and how this use is related to the characteristics of the nests, reproductive parameters and condition of the offspring ”, he highlights based on the doctoral thesis supervised by UÉ researchers, Anabela Belo and João Rabaça, and by Merino Rodriguez Santiago, researcher at the Museo Nacional de Ciencias Naturales, a leading Spanish scientific research institute in the field of natural sciences.

In the study, it is noted that the offspring are affected by parasites in various ways, "through ectoparasites present in nests that establish direct contact with the young". In order to mitigate the negative impacts of the parasites, both the parents and the offspring can adopt different defense mechanisms that will reduce the probability of parasites arrival and relieve contact with these parasites.

The results obtained gave scientific support to previous studies, “but this came to considerably improve knowledge on this topic, including new study variables, new methodologies and new ideas”, says Bárbara Pires, stating that “it was clear that the introduction of aromatic plants in nests benefits the development and condition of the offspring ”

The selectivity of aromatic plants by females and the frequency with which aromatic plants are included in the nests were already known, but not with the level of detail that this study allowed to achieve. Bárbara Pires also stresses in this regard that “biodiversity faces a crisis, amplified by the effects of climate change, and that the variation of these changes will affect the availability of resources” giving as an example the supply of food or materials used in the construction of nests, so “it will be important to witness how species with such specific behaviors will adapt” asks Bárbara Pires.

In conclusion, the UÉ researcher explains that the plants used can influence the characteristics of the nests, reproductive parameters and condition of the young, since these are built by the female and the plants are also incorporated by the female. “If we think of the nest and the plants as an extension of the female's parental care, it makes sense that the" best "nests are those that have more plants or those where plants are used more often" he maintains, in the same way, and assuming that plants have a positive effect on the survival rate of the young and their development, “then it will make sense to think that the" best "nests have more plants and, therefore, create more young and young with better body conditions.

Published in 12.01.2021