During the spring of 2020, bird surveys were conducted in the ornithological reserve Palud. There were 35 breeding species registered. The most numerous species were the Eurasian Blackcap Sylvia atricapilla, the Common Nightingale Luscinia megarhynchos, the Common Blackbird Turdus merula, and the Eastern Subalpine Warbler Sylvia cantillans. A vulnerable breeder of Croatia, the Black-winged Stilt Himantopus himantopus, and a scarce breeder, the Common Shelduck Tadorna tadorna, were also recorded as breeding species.

Gulls are a group of seabirds distributed worldwide that are an important reservoir of Salmonella spp. Salmonellosis is the second most commonly reported gastrointestinal infection in humans, and understanding the role wild birds have in spreading Salmonella can help to improve the health of humans and domestic animals. The mobility and migration capacity of gulls makes them an interesting group for research given their potential role in spreading pathogens. This paper presents the diversity and prevalence of Salmonella spp. in different gull species caught at a landfill in Zagreb in the winter months over a nine-year period from 2014-2022. In total, 1083 cloacal swabs were sampled from six gull species: Black-headed Gull (Larus ridibundus), Yellow-legged Gull (L. michahellis), Caspian Gull (L. cachinnans), Common Gull (L. canus), Lesser Black-back Gull (L. fuscus) and Herring Gull (L. argentatus). The prevalence of Salmonella was 5.82%, and 16 Salmonella serotypes were identified; S. Typhimurium had the highest prevalence (47.62%) followed by S. Enteritidis (12.69%) and S. Infantis (9.52%). To date, 82 Salmonella serotypes have been isolated in research on gulls in Europe, with S. Typhimurium as the most common, followed by S. Agona and S. Enteritidis. In this study, we found three serotypes not previously reported in gulls, S. Yalding, S. Reading and one with the antigenic formula O:17; H:z10; H:e,n,x,z15 (IIIb).

Campylobacter lari is a thermotolerant bacterium that sporadically causes gastrointestinal diseases in humans and can be found in wildlife and the environment. C. lari is an understudied species, especially in wild birds such as gulls. Gulls are potentially good carriers of pathogens due to their opportunistic behavior and tendency to gather in large flocks. During winter and their breeding period, 1753 gulls were captured, and cloacal swabs were taken to be tested for the presence of C. lari. From isolated bacteria, the DNA was sequenced, and sequence types (ST) were determined. Sixty-four swabs were positive for C. lari, and from those, forty-three different STs were determined, of which thirty-one were newly described. The whole genome was sequenced for 43 random isolates, and the same isolates were tested for antimicrobial susceptibility using the broth microdilution method to compare them to WGS-derived antimicrobial-resistant isolates. All the tested strains were susceptible to erythromycin, gentamicin, and chloramphenicol, and all were resistant to ciprofloxacin. Resistance to ciprofloxacin was attributed to a gyrA_2 T86V mutation. Genes connected to possible beta-lactam resistance (blaOXA genes) were also detected.