Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12, 513-529 2025 Publisher: Learning Gate DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate © 2025 by the authors; licensee Learning Gate History: Received: 3 October 2025; Revised: 17 November 2025; Accepted: 21 November 2025; Published: 9 December 2025 * Correspondence: ayoub.elissaoui@usmba.ac.ma Ecological impact of Oued Fez canalisation Morocco on waterbirds biodiversity Ayoub EL ISSAOUI1*, Abderrahim BOUHADDIOUI1, Jamila BAHHOU1 1Sidi Mohamed Ben Abdellah University. Faculty of Sciences Dhar El Mahraz, Laboratory of Biotechnology, Conservation and Valorisation of Bioresources. BP: 1796 Fez-Atlas. Fez-Morocco; ayoub.elissaoui@usmba.ac.ma (A.E.I.) bouhadiwi@gmail.com (A.B.) jamila.bahhou@usmba.ac.ma (J.B.). Abstract: The Oued Fez River crosses northern Fez and historically maintained a permanent marsh that supported both resident and migratory waterbird communities. In 2024, the Sebou Water Basin Agency implemented river-channeling operations to control Pistia stratiotes, an invasive aquatic plant. These interventions altered the hydrological regime and resulted in the complete drying of the wetland area. To assess the ecological consequences of these developments, monthly waterbird surveys were conducted over a three-year period (2022–2024), covering conditions before and after the works. Results indicate a marked decline in avifaunal diversity, with total numbers decreasing from 2,910 individuals in 2022 to 756 in 2024, and species richness falling from 66 to 28, mainly affecting migratory species. A Student’s t- test confirmed a statistically significant difference between the two periods, suggesting that the observed changes are attributable to habitat degradation rather than random variation. The loss of wetland habitat, disruption of hydrological dynamics, and reduction of suitable wintering and feeding areas appear to be the primary drivers of this decline. The study underscores the need for integrated ecological management to balance hydraulic development objectives with the conservation of avian biodiversity. Keywords: Habitat loss, Waterbird diversity, Oued Fez, Pistia stratiotes, Morocco, Urban wetlands. 1. Introduction Among the ecosystems most vulnerable to anthropogenic pressure are urban wetlands [1]. Subjected to drainage and filling operations intended to free up land for construction, they undergo profound and often irreversible alterations to their hydrological dynamics [2, 3]. These transformations disrupt water circulation and retention, reduce soil stabilization, and compromise flood mitigation and groundwater recharge [4]. Ecologically, the degradation of these environments results in the loss of essential habitats for many aquatic, fish, and bird species, leading to a marked decline in biodiversity [5-7]. In Morocco, wetlands are characterized by significant biodiversity, despite their relatively small surface area of approximately 4,000 km², and include nearly 300 natural and artificial sites [8-12], 38 of which are classified as Ramsar sites. Morocco's avifauna comprises 421 recorded species, 240 of which breed in the country [9]. Among these, 95 breeding species are of significant conservation value according to IUCN criteria [9, 13]. The Oued Fez, a tributary of the Oued Sebou, is a natural urban wetland of great ecological importance, particularly for aquatic birdlife. Flowing through the city of Fez, this watercourse plays an essential role in maintaining biodiversity [14]. However, it is now severely degraded by urban developments that channel its flow. Various interventions to combat Pistia stratiotes have profoundly altered the hydrological regime of the Oued Fez [15, 16], leading in particular to the disappearance of the marshland area that provided a habitat for many species of aquatic birds. It is in this context that our study is being conducted, with the 514 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate aim of studying the phenological status of the site's aquatic bird population through monthly monitoring from January 2022 to December 2024, as well as assessing the impact of developments on its biodiversity. 2. Materials and Methods 2.1. Presentation of the Site The Oued Fez is a watercourse that flows through the city of Fez between parallels 33°30' and 34°08' N, and meridians 4°54' and 5°09' W, fed by karstic resurgence springs at Ras El Ma (Fig. 1). This watercourse plays a fundamental hydrological role, collecting water from the Fez catchment area before joining the Oued Sebou. This is a subsidence region filled with Neogene deposits, bordered to the south by the Jurassic limestones and dolomites of the Middle Atlas, and to the north by the Prerif formations [17, 18]. The climate is semi-arid, characterized by cold, wet winters and hot, dry summers. The average annual rainfall is 494 mm, while the average temperature is around 17.5°C [19]. The hydrological regime of the Oued is characterized by irregular flow that varies according to the seasons and years, depending on the weather conditions in the region. Figure 1. Location of the study area. Our study area is a marshy depression that receives water from adjacent springs located mainly on the right bank, as well as from rainfall. 515 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate 2.2. Bird Census To study the phenology of the avifauna of Oued Fez, census campaigns were conducted from January 2022 to December 2024 on a bi-monthly to monthly basis, depending on the nesting, migration, and/or wintering periods across the entire study site (Fig. 1). The direct counting method adopted was that of Lamotte and Bourlière [20], which involves counting individuals when the group does not exceed 200 individuals. The census was carried out by two observers using binoculars (12×50) and a high-magnification camera (Nikon Coolpix P1000). Species identification was carried out using ornithological guides [21-23]. 2.3. Avifauna Population Structure The structure of populations in the study area was examined using various ecological indices that reflect population balance: total abundance, species richness, Shannon and Weaver diversity index [24], equitability index, Student's t-test, and factor analysis of correspondences. Shannon and equity index: The Shannon index was calculated using the following formula: H'= -∑ (ni/ N) x Log2 (ni/N) Where: N = Sum of the numbers of all species ni = Population size of species i The results are expressed in bits/individual. Equity index is determined using the following formula: E = H' / H'max, where H'max represents the theoretical maximum diversity of the population. This value corresponds to a situation in which individuals are distributed perfectly equally among all species and is calculated according to the relationship H'max = Log₂(S), where S denotes the total species richness, i.e., the number of species present in the environment. 2.4. Student's T-Test for Paired Samples This test compares the means of two measurements taken on the same individuals or experimental units. It determines whether the mean difference between these two series of measurements is statistically significant [25]. It is represented by the following equation: 𝑡 = �̄�𝟏−�̄�𝟐 √ 𝒔𝟏 2 𝒏𝟐 + 𝒔𝟐 2 𝒏𝟐 Where: 2.5. Factor Analysis of Correspondences Census correlation, the multivariate statistical method PCA was used to analyze annual variations in aquatic bird species at the study site and to establish a correlation between the presence of bird species (observed variables) and observations (census dates). 516 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate 3. Results 3.1. Specific Composition of the Bird Population In 2022, there was a significant number of birds, reaching 2,887. This number decreased by half to 1,551 individuals in 2023, then fell sharply to 758 individuals in 2024 (Table 1). Monthly monitoring of birdlife in the Oued Fez area from January 2022 to December 2024 identified 67 species of water birds, divided into 18 families. The Scolopacidae and Anatidae families are the most abundant, with 23% and 16% of species, respectively, followed by Ardeidae at 11% and Laridae at 7.4%. The species richness within these families represented a significant proportion of the species counts reported at the national level: 80% for Ardeidae, 69% for Scolopacidae, 52% for Anatidae, and 44% for Rallidae. The observations also recorded the presence of species of international importance such as the coot, a species found mainly in Morocco and Spain; the white-headed duck (endangered); the tufted duck (vulnerable); as well as the ferruginous duck, the marbled teal, the bar-tailed godwit, the black-tailed godwit, the red knot, and the dunlin (near threatened). Coastal species such as the sanderling and the ringed plover were also observed (Table 1). 517 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate Table 1. List of bird species with their phenological status and conservation status at the study site during the three-year monitoring period (2022 to 2024). Orders Families Scientific names Phenological status Conservation status 2022 2023 2024 Total Percentage A n se ri fo rm es A n at id ae Oxyura leucocephala Scopoli, 1769 WV; RB; PM? EN 5 1 0 6 0.09% Spatula clypeata Linnaeus, 1758 WV; PM; OB LC 68 13 0 145 2.22% Anas crecca Linnaeus, 1758 WV; PM LC 85 27 0 195 2.99% Anas platyrhynchos Linnaeus, 1758 RB; WV LC 174 72 28 358 5.48% Spatula querquedula Linnaeus, 1758 PM; OW LC 7 4 0 11 0.17% Mareca strepera Linnaeus, 1758 WV; PM; OB LC 66 8 0 102 1.56% Aythya ferina Linnaeus, 1758 WV; PM; OB VU 75 22 0 97 1.49% Aythya nyroca Güldenstädt 1770 RB 13 0 0 16 0.25% Tadorna ferruginea Pallas, 1764 RB LC 1 0 0 1 0.02% Netta rufina Pallas, 1773 RB 4 0 0 4 0.06% Marmaronetta angustirostris Ménétries, 1832 RB; WV; PM NT 2 2 0 5 0.08% 500 149 28 940 14.40% Ciconiiformes Ardeidae Ardea alba Linnaeus, 1758 WV; PM LC 2 0 0 3 0.05% Ardea cinerea Linnaeus, 1758 PM; WV; OB LC 17 22 8 62 0.95% Ardea purpurea Linnaeus, 1766 PM; BM; OW LC 2 2 0 5 0.08% Nycticorax nycticorax Linnaeus, 1758 PM; BM; WV LC 17 20 37 84 1.29% Bubulcus ibis Linnaeus, 1758 RB; PM; WV LC 219 193 198 627 9.61% Egretta garzetta Linnaeus, 1766 RB; PM; WV LC 145 79 100 370 5.67% Ardeola ralloides Scopoli, 1769 BM; RB? PM; W LC 63 71 51 199 3.05% Botaurus minutus Linnaeus, 1766 BM; RB? PM 9 5 2 18 0.28% 474 392 396 1368 20.96% Ciconiidae Ciconia ciconia Linnaeus, 1758 PM; BM; WV LC 47 121 46 224 3.43% 47 121 46 224 3.43% Phoenicopteridae Phoenicopterus roseus Pallas, 1811 PM; WV; RB LC 1 0 0 1 0.02% 1 0 0 1 0.02% Threskiornithidae Platalea leucorodia Linnaeus, 1758 PM; WV; RB LC 1 0 0 1 0.02% Plegadis falcinellus Linnaeus, 1766 PM; WV; OB LC 70 55 41 181 2.77% 71 55 41 182 2.79% Rallidae Fulica spp 28 0 0 40 0.61% Fulica atra Linnaeus, 1758 RB; WV LC 396 78 5 771 11.81% Fulica cristata Gmelin, 1789 RB LC 406 93 58 874 13.39% Gallinula chloropus Linnaeus, 1758 RB; WV LC 124 157 54 393 6.02% Porphyrio porphyrio Linnaeus, 1758 WV; PM; OB LC 5 99 27 147 2.25% 518 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate 959 427 144 2225 34.09% Laridae Chlidonias niger Linnaeus, 1758 PM LC 2 0 0 2 0.03% Charadriiformes Chlidonias hybrida Pallas, 1811 PM; WV; OB LC 5 0 0 5 0.08% Gelochelidon nilotica Gmelin, 1789 PM LC 12 1 0 13 0.20% Chroicocephalus ridibundus Linnaeus, 1766 WV; PM; RB LC 3 0 0 12 0.18% Sternula albifrons Pallas, 1764 BM; PM; OW LC 9 4 0 13 0.20% 31 5 0 45 0.69% Scolopacidae Calidris spp 0 0 0 4 0.06% Calidris alba Pallas, 1764 PM; WV LC 1 1 0 2 0.03% Calidris alpina Linnaeus, 1758 PM; WV LC 2 3 0 5 0.08% Calidris canutus Linnaeus, 1758 PM; WV NT 2 0 0 2 0.03% Calidris ferruginea Pontoppidan, 1763 PM, WV NT 4 0 0 4 0.06% Calidris minuta Leisler, 1812 PM; WV LC 6 0 0 6 0.09% Calidris temminckii Leisler, 1812 PM; WV LC 4 0 0 4 0.06% Tringa spp 2 0 0 4 0.06% Tringa erythropus Pallas, 1764 PM; WV LC 5 4 0 11 0.17% Tringa glareola Linnaeus, 1758 PM; WV LC 10 14 3 29 0.44% Tringa nebularia Gunnerus, 1767 PM; WV LC 22 14 3 60 0.92% Tringa ochropus Linnaeus, 1758 PM; WV LC 5 4 1 10 0.15% Tringa tetanus Linnaeus, 1758 PM; WV; OB LC 7 2 0 14 0.21% Actitis hypoleucos Linnaeus, 1758 PM; WV LC 25 17 9 61 0.93% Gallinago Gallinago Linnaeus, 1758 PM; WV LC 23 3 0 41 0.63% Calidris pugnax Linnaeus, 1758 PM LC 55 32 0 99 1.52% Limosa lapponica Linnaeus, 1758 PM; WV NT 2 1 0 3 0.05% Limosa limosa Linnaeus, 1758 PM; WV NT 0 0 4 6 0.09% 175 95 20 365 5.59% Charadriidae Charadrius alexandrines Linnaeus, 1758 RB; PM; WV LC 5 2 6 19 0.29% Charadrius dubius Scopoli, 1786 RB; PM; WV LC 68 48 16 142 2.18% Charadrius hiaticula Linnaeus, 1758 PM; WV LC 0 0 0 2 0.03% 73 50 22 163 2.50% Charadriiformes Glareolidae Glareola pratincola Linnaeus, 1758 PM; BM; OW LC 142 8 0 155 2.37% 142 8 0 155 2.37% Recurvirostridae Himantopus Himantopus BM/RB; PM; WV LC 106 70 37 271 4.15% Linnaeus, 1758 106 70 37 271 4.15% Pelecaniformes Phalacrocoracidae Phalacrocorax carbo Linnaeus, 1758 WV LC 132 25 0 186 2.85% 132 25 0 186 2.85% 519 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate Podicipediformes Podicipedidae Podiceps cristatus Linnaeus, 1758 RB; WV LC 19 4 1 27 0.41% Tachybaptus ruficollis Pallas, 1764 RB LC 54 57 0 137 2.10% 73 61 1 164 2.51% Pandioniformes Pandionidae Pandion haliaetus Linnaeus, 1758 PM; WV; RB LC 4 3 0 7 0.11% 4 3 0 7 0.11% Falconiformes Accipitridae Elanus caeruleus Desfontaines, 1789 RB, BM LC 2 1 0 5 0.08% Circus aeruginosus Linnaeus, 1758 RB; WV; PM LC 11 2 0 15 0.23% Hieraaetus pennatus Gmelin, 1788 RB LC 2 1 0 3 0.05% 15 4 0 23 0.35% Falconidae Falco peregrinus Tunstall, 1771 RB LC 2 0 0 2 0.03% Falco tinnunculus Linnaeus, 1758 RB LC 10 2 2 16 0.25% 12 2 2 18 0.28% Burhiniformes Burhinidae Burhinus oedicnemus Linnaeus, 1758 RB; WV; PM LC 5 18 3 27 0.41% 5 18 3 27 0.41% Passeriformes Motacillidae Motacilla alba Linnaeus, 1758 WV; RB; PM LC 47 22 9 83 1.27% Motacilla alba subpersonata Meade- Waldo, 1901 RB LC 2 1 1 5 0.08% Motacilla cinerea Tunstall, 177 PM; RB; WV LC 6 4 7 20 0.31% Motacilla flava Linnaeus, 1758 PM; BM/RB; WV LC 12 39 1 55 0.84% 67 66 18 163 2.50% 2887 1551 758 6527 100% Note: (*) Species with significant conservation status; (**) Species of coastal origin. Phenological status: (RB: Resident breeder, WV: Winter visitor, PM: Passage migrant, BM: Breeding migrant, OB: Occasional breeder; PAV: Palearctic vagrant) and conservation status according to the IUCN (EN: Endangered, LC: Least concern, NT: Near threatened). 520 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate From 66 in 2022 to 52 in 2023, then dropping sharply to 28 in 2024. The Shannon index fell from 3.28 in 2022 to 3.16 in 2023 and 2.55 in 2024, indicating a significant loss of species diversity, both in terms of richness and distribution of individuals. These results show that 2022 was the most favorable year for biodiversity, while 2024 saw a significant decline in biological diversity (Table 2). The equity index remains relatively stable (0.78 in 2022, 0.79 in 2023, and 0.76 in 2024), despite the sharp decline in the number of species in 2024, as those that remain are distributed evenly. Table 2. Species richness, Shannon biodiversity index, and equity index in 2022, 2023, and 2024. Year 2022 2023 2024 Total Specific richness 66 52 28 67 Shannon index 3.28 3.16 2.55 3.17 Equity index 0.78 0.79 0.76 0.75 The species recorded belong to different phenological categories, namely: winter visitors, summer visitors, migrants, breeders, and non-breeders, which can be described as follows: 1. Migrants, winter visitors, and summer visitors: these are species that are present all year round but do not breed locally, such as the grey heron and the little ringed plover. 2. Migrants and winter visitors: these are species that are absent in summer and present in autumn, winter, and spring, such as the common teal and the northern shoveler. 3. Strict winter visitors: these are species observed exclusively during winter, such as the great cormorant and the great egret. 4. Migratory breeders: these are summer breeders observed in summer, such as the collared pratincole. 5. Non-breeding summer visitors: these arrive during the summer without breeding, such as the Sandwich Tern and the Whiskered Tern. 6. Sedentary breeders: localised breeders, found throughout the year. This is the case for the coot. 7. Sedentary, migratory, and wintering breeders: these are sedentary birds that breed on the site, joined by passing migrants and wintering birds, such as the common coot, mallard, moorhen, purple swamphen, and black-winged stilt. 8. Strict migrants: these are species that have been observed during postnuptial migration from July to October and prenuptial migration from March to May; Temminck’s stint, red knot, and green sandpiper. 3.2. Interannual Variation in Bird Numbers Ornithological monitoring showed a very significant interannual variation in the number of each species observed during the study period. The highest percentages of the population are attributed to the crested coot (13.39%), the common coot (11.81%), cattle egret (9.61%), moorhen (6.02%), little egret (5.67%), mallard (5.48%), and black-winged stilt (4.15%). These seven species alone account for 56.13% of the total bird population (Table 2). 521 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate Figure 2. Temporal variation of representative species at the site. 522 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate 3.3. Paired Samples Student's T-Test The biodiversity averages show a significant decrease from 2022 to 2024, with average values falling from 188.33 in 2022 to 101.8 in 2023, then to 50.2 in 2024. This decrease is confirmed by the Student's t- test (t = 2.233; p = 0.042 between 2022 and 2023, t = 2.735; p = 0.016 between 2023 and 2024, and t = 2.502; p = 0.025 between 2022 and 2024), indicating that these differences are statistically significant. The high correlations between the series (r = 0.889, 0.836, and 0.572) show a consistent trend (Table 3). Table 3. Results of Student's t-tests comparing biodiversity between the years 2022, 2023, and 2024 (means, variances, correlations, t- values and p-values). Comparison Mean 1 Mean 2 Variance 1 Variance 2 Observa- tions Correlation (r) T- statistic p (bilateral) 2022 – 2023 188.33 101.8 65 108.81 17 545.46 15 0.889 2.233 0.042 2023 – 2024 101.8 50.2 17 545.46 10 493.6 15 0.836 2.735 0.016 2022 – 2024 188.33 50.2 65 108.81 10 493.6 15 0.572 2.502 0.025 3.4. Principal Component Analysis 1. In 2022, principal component analysis shows that axes 1 and 2 of the variables account for 56% of the total information, with the four most representative bird groups being (Figure 3 (a-b)). Anatidae, Podicipedidae, Rallidae, and Recurvirostridae are mainly positioned on the winter axis, corresponding to the months of November to February, a period marked by the arrival of Palaearctic migrants exploiting deep water bodies. Ardeidae and Threskiornithidae, on the other hand, cluster around the spring and summer months (March to August), reflecting their nesting activity in wetlands with emergent vegetation. Charadriidae and Scolopacidae appear mainly during the transition period (September–October), when falling water levels expose muddy areas. The common coot Fulica atra, associated with the wintering group, confirms its status as a breeding resident, reinforced in winter by migratory arrivals. This structure reflects the strong dependence of functional guilds on seasonal habitat variation. 2. In 2023, principal component analysis shows that axes 1 and 2 of the variables account for 57% of the total information. The four most representative groups of birds are (Figure 3 (c-d)). This year, the factorial configuration remains similar, but the temporal separation between groups is more pronounced. The months of January to March remain associated with Anatidae and Podicipedidae, confirming the winter predominance of these aquatic families. Ardeidae and Threskiornithidae dominate the spring and summer period (April to August), indicating an intensification of reproductive activity, as in the case of the glossy ibis and the little egret. Charadriidae and Scolopacidae, on the other hand, are concentrated in late summer and early autumn, corresponding to post-nuptial migration. The red-crested coot Fulica cristata is more prevalent in spring, highlighting its local reproduction and attachment to stabilized marsh areas. This spatial and temporal distribution reflects an increased synchronization between the biological cycles of the species and the hydrological conditions of the site. 3. In 2024, principal component analysis shows that axes 1 and 2 of the variables account for 55.7% of the total information, with the four most representative bird groups being (Figure 3 (e-f)). Anatidae, Podicipedidae, and Rallidae remain dominant in winter (December to February), while Ardeidae and Threskiornithidae remain typical of spring–summer. Charadriidae, Scolopacidae, and Burhinidae remain associated with autumn transition periods, confirming their dependence on water level variation. 523 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate Figure 3. Principal component analysis of the bird population at Oued Fez from 2022 to 2024. 4. Discussion Monthly monitoring of birdlife in the Oued Fez area from January 2022 to December 2024 enabled us to identify 67 species of water birds, one of the highest numbers in Moroccan wetlands, exceeding the Smir complex, which recorded 58 species between 2005 and 2009 [26] and also higher than those recorded in the Rabat Bouznika coastal area between 1999 and 2001 with 24 species [27] and the Middle 524 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate Atlas, which is home to only 24 species [28]. However, it remains lower than those recorded in Idriss Premier with 78 species and in the coastal wetlands of Martil, which has 93 [29]. In Algeria, 79 species were counted in the Setif wetland eco-complex [30] and 21 species in Oum El Boughi in the north of the country [31]. In Tunisia, 34 species were observed in the Douz wetlands in the south [32]. In Italy, 60 species have been observed in the Sardinian wetlands [33]. In Turkey, 67 species have been recorded in the western part of the country (Anatolia) [34]. Analysis of the specific composition highlights the precise organization of waterbird communities according to their phenological status [35]. There are three main groups: breeding birds, winter visitors, and migratory birds passing through. In addition to these groups, there are sedentary species or species with mixed status, such as the coot, the crested coot, the mallard, the moorhen, and the little egret, which are present all year round. This distribution demonstrates the functional and seasonal diversity of birds on the site. Confirmed by Student's t-test, the Oued Fez area has suffered significant degradation of its natural habitats, mainly due to hydraulic developments involving the canalization of the main watercourse, with the aim of combating the spread of the invasive plant Pistia stratiotes. These changes have led to the reduction of the marshland area and its total disappearance in 2024 (Figure 4), fragmentation of habitats, and alteration of hydrological regimes, compromising the conditions necessary for the reproduction, feeding, and resting of waterbirds [2, 16, 36]. As a result, local biodiversity has shown a marked decline, both in terms of species richness and abundance, reflecting the sensitivity of these ecosystems to anthropogenic disturbances [11, 14, 37]. Figure 4. Changes to the water body from 2021 to 2024. 525 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate According to census results, the degradation of this habitat particularly affects migratory and wintering birds, especially waders, whose presence is closely linked to the availability of resting and feeding areas [33, 38, 39]. The disappearance of land areas, the canalization of riverbanks, and the disruption of mudflats generally lead to a significant reduction or even total disappearance of habitats favorable to birdlife, limiting their migratory stopovers and thus compromising their annual migration cycle [33, 40, 41]. The presence of Pistia stratiotes, used as a perch by large wading birds for fishing, particularly the Squacco Heron, Little Egret, Night Heron, Glossy Ibis, Little Bittern, Cattle Egret, Grey Heron, and Purple Heron, encourages the presence of these species in the site despite the developments. On the other hand, this invasive plant limits the activities of the duck group, mainly divers, by reducing the area of transparent water. Figure 5. View of the study site before and after hydraulic improvements. Numerous wetland creation and restoration projects have been carried out in recent decades [40, 42- 44] but wetland management does not always produce the expected results [45]. It has been reported that foraging rates of waterbirds in managed habitats are not as high as those observed in natural sites [46]. Managed restored habitats are not used by the same species as natural habitats [47], and constructed habitats can only support species of interest for a limited period, as plant succession subsequently alters habitat characteristics [48]. Therefore, a better understanding of the impact of habitat management on waterbirds is needed to develop a more effective strategy for the conservation of wetlands and waterbirds. However, habitat loss is the main threat to biodiversity, leading to population decline and the extinction of many species [49, 50]. More than half of wetlands have disappeared over the last century [42] and the remaining sites often suffer varying degrees of degradation due to anthropogenic pressures, including urbanization, which alters natural landscapes and fragments habitats [36, 51, 52]. This 526 Edelweiss Applied Science and Technology ISSN: 2576-8484 Vol. 9, No. 12: 513-529, 2025 DOI: 10.55214/2576-8484.v9i12.11381 © 2025 by the authors; licensee Learning Gate situation is even more concerning as wetlands are particularly sensitive to climate change and land use, causing differential effects on waterbird species and affecting their abundance and distribution [53-55]. 5. Conclusion The Oued Fez represents a site of high ecological importance for aquatic bird species, supporting up to 67 species, including the white-headed duck Oxyura leucocephala, the common pochard Aythya ferina, and the ferruginous duck Aythya nyroca. The area is particularly critical for migratory and breeding species, such as the red-crested coot Fulica cristata, the common coot Fulica atra, the common pochard Aythya ferina, the collared pratincole Glareola pratincola, and the black-winged stilt Himantopus himantopus, which rely on its habitats for reproduction, foraging, and resting. However, development work in 2024 to combat Pistia stratiotes led to a significant deterioration of these environments, resulting in a decrease in diversity from 3.28 in 2022 to 2.55 in 2024, the number of species from 66 in 2022 to 28 in 2024, and the total population, which fell from 2,887 to 758 individuals, the majority of which are Ardeidae. These ill-considered anthropogenic transformations have altered the ecological balance of the site and weakened the most vulnerable populations, which have disappeared completely from the site, such as the white-headed duck, the common pochard, the ferruginous duck, the ruff, and the collared pratincole. It appears essential to carry out exhaustive and integrated studies of the entire ecosystem in consultation with all stakeholders before any development actions are taken, to reconcile development and the preservation of biodiversity, and to guarantee the ecological sustainability of sites of high ornithological value. 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