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Table 2 Duration of maximum activity periods (minutes) in 10-days intervals as recorded by three different recording techniques

From: The influence of night length: Activity of the northern bat Eptesicus nilssonii under conditions of continuous light in midnight sun compared to a southern population

Time

IR detection

Visual counts

Ultrasound rec.

period

Løvhaug

Bardu

Saltdal

Løvhaug

Troms

Saltdal

Troms

Frafjord

11-20 May

       

248

21-31 May

       

316

1-10 June

       

286

11-20 June

       

272

21-30 June

275

  

244

  

254

313

1-10 July

299

 

337

304

167

240

433

312

11-20 July

368

223

300

314

370

257

433

338

21-31 July

348

242

326

356

394

285

357

384

1-10 Aug.

376

357

330

387

323

 

345

429

11-20 Aug.

440

405

470

361

465

454

315

454

21-31 Aug.

388

416

501

470

508

439

430

505

1-10 Sept.

   

595

 

459

513

568

11-20 Sept.

      

524

538

21-30 Sept.

      

568

 
  1. The techniques were: IR detection at the roosts Løvhaug, Bardu and Saltdal, visual counts at the roost Løvhaug, at all other roosts in Troms combined and at two roosts in Saltdal, and ultrasound recordings in Troms and in Frafjord. The duration is the time between the first exit/pass and the last return/pass