Well-being and mental health research is a rapidly growing field of study within the area of birds and ecology. One of the prominent ideas is that being outside in nature often leads to increased mental well-being among recreationists, with research typically focusing on the characteristics of the area or landscape. Earlier studies have also theorized that biodiversity is one of the main drivers of this phenomenon [see, for example, but not exclusively, Adjei and Agyei (2015); De Vries and Snep (2019); Houlden et al. (2021)]. Research has shown mixed results between the effects of biodiversity, perceived biodiversity, and experimentally increased biodiversity. We propose here that birds, as a key component of an area’s characteristics, play an important role in this. Birds can be perceived both directly and unconsciously. They are a taxonomic group that is easily recognised and observed by people (Cox and Gaston, 2015), regardless of ornithological knowledge. Additionally, they are a common and well-studied taxon, sensitive to anthropogenic influences (Gregory et al., 2008) and therefore valuable indicators of biological diversity, ecological conditions, and environmental status (Randler and Koch, 2025). Their species characteristics are closely linked to their habitat and ecosystem services (Sekercioglu, 2006), and they are well-suited to connect urban residents with nature (Belaire et al., 2015). In contrast to many mammals and reptiles, birds are mostly diurnal, and many are found in urban areas. Some are also extremely common in city settings.

Birds have been linked to increased happiness (White et al., 2023) and improved mental health (Xie et al., 2023) in people. Their sounds play a crucial role (Chen et al., 2022) in stress relief, though not all bird sounds are equally beneficial (Ratcliffe et al., 2013). Earlier studies often focused on bird species richness (Methorst et al., 2021). Some also looked at the effects of bird observation (Cox and Gaston, 2015), or bird song (Stobbe et al., 2022), sometimes even attempting to artificially increase bird song to foster well-being (Ferraro et al., 2020). However, some research has found no association of bird species richness with people’s mental well-being (Cox et al., 2017; Taylor et al., 2018). Some only found a relationship with perceived bird diversity instead of actual biodiversity measures (Dallimer et al., 2012). This inconsistent relationship between bird diversity, perceived bird diversity, and human mental health (Lovell et al., 2014) renders it difficult to measure if and how conservation efforts in nature could boost mental well-being. Since experiencing biodiverse urban green spaces can evidently bring joy (Douglas and Evans, 2021) and generally has positive effects (Carrus et al., 2015), it’s important to look beyond general assessments of bird diversity and maybe look at the composition of bird species in an area.

To our knowledge, no studies have yet assessed the bird species characteristics and traits that may be responsible for the mental well-being of recreationists. Additionally, only a few studies have considered that not all bird species equally affect people [see, for example, Fisher et al. (2023); Garnett et al. (2018); Randler and Koch (2025); Randler et al. (2023); Ratcliffe et al. (2013)]. This might be important because there is a large variation in the perception, likeability, and preferences of bird species (Albert et al., 2018; Veríssimo et al., 2014; White et al., 2023) as well as in the bird species themselves. Aesthetically pleasing animals are often considered charismatic (Prokop et al., 2025; Veríssimo et al., 2014), and small and vividly colored birds are often perceived as more beautiful (Haukka et al., 2023; Santangeli et al., 2023). Most people also share a preference for birdsong (Chen et al., 2022), but some songs and calls can also annoy urban residents (Belaire et al., 2015; Pejchar et al., 2025). Some bird species, such as the hooded crow, for example, are also associated with problems such as trash scattering, noise disturbance, and aggressive behavior (Kövér et al., 2022). Lišková and Frynta (2013) have already emphasized that finding the traits that determine human preference towards birds may help promote conservation programs. Earlier studies on flagship species have suggested certain species characteristics of liked animal species, with a high body mass (Santarém et al., 2019; Smith et al., 2012), and a large body size often being linked to charisma (Albert et al., 2018; Callaghan et al., 2021).

Finding the species traits important for human mental well-being may explain the discrepancies between studies, since not all birds are present in all study areas similarly. The study by Garnett et al. (2018), for example, found a preference for small colorful birds with melodious song, but participants then nominated mostly large and well-known species as most attractive. According to Haukka et al. (2023), aesthetic attraction is dependent on a set of features that make something interesting or likable, usually composed of visual and emotional cues. This is why many liked species exhibit a bright appearance, colors, or color patterns (Santarém et al., 2019; Veríssimo et al., 2014). Aesthetic attraction seems to be highest for smaller birds, with vivid colors and extreme ornaments (Santangeli et al., 2023). Other factors seemingly playing a role are visibility, rarity, familiarity, or encounter rate (Santangeli et al., 2023; Schlegel and Rupf, 2010; Veríssimo et al., 2014). Some charismatic species are also considered “sweet” or “cute” (Albert et al., 2018; Borgi et al., 2014). The concept of cuteness is based on the baby schema by Lorenz (1943), which sums up characteristics that are supposed to trigger an innate caring behavior in humans. These characteristics consist of a large head in relation to body size, short and thick extremities, a large set of eyes, a large, rounded forehead, and round, protruding, chubby cheeks (Lorenz, 1943). Animals exhibiting the baby schema are often perceived as cute and draw the viewer’s attention (Albert et al., 2018). Bird species perceived as cute elicited a higher willingness to protect, as well as a bright coloration (Randler and Koch, 2025).

We hypothesize that the human perception of birds is strongly linked to mental well-being, and therefore, the species composition in an area may determine the mental well-being benefits received when visiting. In this study, we investigate the link between human perception of bird traits and well-being to determine if and how species composition in recreational areas affects place attachment and well-being of visitors.

This study consists of two parts. First, a survey was conducted among people in recreational areas to assess their mental well-being. In the same areas, the bird species were recorded. In a second step, the well-being data were related to the bird species characteristics.

The factor values for the HRV of the respective bird species are shown in Table 3. The bird species are ranked from highest to lowest by their HRV_species score. A high HRV_species score means a positive evaluation of species traits.

For the correlation with mental well-being, the HRV significantly correlated with satisfaction (Table 4). However, the other correlations falied significance only marginally.

With increasing HRV_place, satisfaction with the visit increased significantly (Figure 1). This also means that bird species with a high HRV_species (for example, Erithacus rubecula or Cyanistes caeruleus) have a positive effect on satisfaction after the visit. In contrast, species like Carrion Crow (Corvus corone) or Feral Pigeon (Columba livia f. domestica) negatively affect the satisfactory value of a given place. By using the species frequency in the HRV_place calculation, we were able to account for mass aggregations, which are often found in geese, pigeons, or crows, and which are a reality for urban parks.

We here propose a new measure, the Human Restoration Value, to assess the beneficial influence of birds on human well-being. For this value, bird species traits were combined into one value and then related to the mental well-being of humans. This method could potentially be used for many other conservation questions, as discussed below. Each bird species was assigned a value that is based on previous studies on likeability, pleasantness, and attractiveness. Thus, more likable species receive a higher value. This factor can now be used to determine which bird species are perceived favorably by people.

Moreover, based on field work on 40 different places, we were able to assign a well-being value based on the species traits and the bird diversity to each of the areas. This value has been connected to on-site data of well-being in human participants to investigate how species composition affects mental well-being.

Bird species receiving a higher HRV score are mostly species commonly rated as cute, colorful, visually attractive, and with a nice song. Therefore, it is not surprising that this factor significantly correlates with satisfaction. High biodiversity levels are theorized to help with psychophysiological stress recovery, according to the Stress Reduction Theory [= SRT (Ulrich, 1983; Ulrich et al., 1991)]. Additionally, spending time in nature, according to the Attention Restoration Theory (ART), facilitates recovery from attentional fatigue (Kaplan and Kaplan, 1989; Kaplan, 1995). Areas with more beneficial bird species could therefore help with stress reduction and restoration.

Bird song has been associated with stress reduction (Ratcliffe et al., 2013), being able to buffer the negative effects of traffic noise (Uebel et al., 2022), and improving anxiety (Stobbe et al., 2022), making them a very important part of urban soundscapes. A perceptively beautiful bird song is important for the HRV and mental well-being of people, since sounds are one of the most important factors for stimulating well-being responses (Fisher et al., 2023), underscoring the notion that birds singing beautifully have a positive impact and birds screaming or warning have a more negative one. Bird diversity is also often perceived by humans in the form of bird song (Ferraro et al., 2020).

The appearance of a bird species, on the other hand, is also very important as the second way in which people mostly perceive birds: visually. In the study by Fisher et al. (2023), colors and behavior followed behind sound as a determinant of well-being. Attractive birds are colorful, with a bright appearance, and big ornaments (Santangeli et al., 2023; Santarém et al., 2019; Veríssimo et al., 2014). Bigger birds, on the other hand, are often seen as less attractive (Santangeli et al., 2023). These differing factors have to be kept in mind when looking at the “attractiveness” of birds, since attractiveness is a subjective feeling. This is why we added cuteness, brightness, and the beauty of song as variables. All of them are variables, which are subjectively perceived by people experiencing birds.

The HRV is correlated with the well-being variable satisfaction. Emotions, on the other hand, as well as recalled restoration, and the two place-attachment scales are not. Place attachment is strongly linked to perceived restorativeness and perceived restorative potential of an area (Menatti et al., 2019). It consists of two constructs: place attachment identity and place attachment recovery, with the place attachment recovery scale asking for feelings of freedom, clear head, and health (Bryce et al., 2016). Differing to that, recalled restoration asked for feelings of being refreshed (Young et al., 2020). Therefore, beautiful bird song, visual attractivity, cuteness, and brightness do not actually influence refreshment or positive emotions, but satisfaction with a visit. Therefore, bird species like Erithacus rubecula or Cyanistes caeruleus may themselves have a positive impact, or they go together with positively connoted habitats or structures. This could be since people do not consciously experience bird diversity in the study areas but more unconsciously (Vanhöfen et al., 2025, Vanhöfen et al., 2022), and needs to be studied further. Also, the sheer amount of positively perceived birds present in the area could play a role, since areas with high numbers of bird species are also more satisfying to live in, which is an unconscious mechanism (Hepburn et al., 2021).

As can be seen in Figure 1, two areas especially have a negative impact. These two parks especially present with large aggregations of “negative” species, resulting in a very low HRV_place. One location, for example, had more than 100 greylag geese (Anser anser) aggregating, and another had a flock of more than 100 feral pigeons (Columba livia f. domestica). This is important to note, since birds accumulating in large groups could also be perceived as threatening, especially if they are big and noisy. Many abundant species that form large aggregations, like geese, pigeons, and corvids, are associated with aggression (Belaire et al., 2015), dirt/defecation (Leong et al., 2020), and disease transmission (Pejchar et al., 2025). Especially large birds, like greylag geese, egyptian geese (Alopochen aegyptiaca), mute swans (Cygnus olor), and great cormorants (Phalacrocorax carbo), are often perceived as a nuisance since they are loud, do not sing beautifully (Lukanowski, 2023), and oftentimes, people are even scared of them. These accumulations of birds need to be considered, which is why we used the species frequency in calculating our factor. But this is also one of the limitations of this analysis, since these two parks have a high impact on our analysis and therefore need not be overlooked.

The large body size of birds has not been connected to a higher willingness to protect in earlier studies on birds (Randler and Koch, 2025), which is probably why birds with a low factor score are less beneficial for our mental well-being. On the other hand, colorful, cute birds increase positive feelings, especially in combination with beautiful bird song.

To conclude, attractive birds have a positive effect on people’s mental well-being, namely satisfaction. This is important to know for improving human mental health and biodiversity conservation. Protecting aesthetically attractive and nicely singing species helps not only nature but also society. These birds can possibly function as a flagship or umbrella species, leading to conservation benefits for their whole habitat. It has been shown before that charisma and aesthetic attractiveness of species impact the allocation of conservation funding and efforts (Garnett et al., 2018; Lišková and Frynta, 2013). But also, some important flagship species, especially with birds, are dull-looking, small species, strongly impacted by humans. The HRV, as we propose it, is probably not a useful measure for these species. It is a tool for urban species, able to enhance people’s awareness of the benefits of biodiversity. If a bird species has as high HRV as we propose it, it is aesthetically attractive, has a beautiful song, is cute, and colorful. They are species that are able to elicit interest in people, even without a strong conservation background, and are a gateway into conservation and biodiversity awareness. It can also be a reason for planners to improve urban green spaces to attract these species and, therefore, not only create habitat for birds but also improve human mental well-being. But the method of calculating the HRV can surely be used for other applications as well. Using more or other variables in the calculation could help explore other patterns. For example, habitat affinity, foraging strategy, and nest types could be tested for differences between groups, conservation success, among other things. Future studies might therefore investigate a relationship between the HRV and other metrics, including population status, IUCN ranking of certain species, or shed light on relationships between conservation and HRV.

In the context of this study, it is essential to acknowledge that there is also a widely recognized connection between culture and the perceived value or awareness of biodiversity (Ladle et al., 2019; Millard et al., 2021). In many cultures, birds are connected to religion/folklore. This means that one species could be perceived as positive in one country and negative in another. Hummel et al. (2015), for example, found that there are significant differences between countries regarding the presence of myths surrounding birds.

This is why the present results need to be taken to a larger scale in further studies, in addition to being carefully interpreted in a cultural context. Right now, this study presents a method of analyzing bird species traits and connecting them with the well-being of recreationists, based in south-west Germany. Expanding the survey to other countries would result in more robust results regarding the connection of the HRV to human well-being. Nevertheless, our results are a promising start, showing that species traits of birds are indeed related to the human experience in recreational areas.