Can hours accumulated in a glider count towards the 1500 hours for an ATP certificate?
According to my reading of 14 CFR 61.159, glider hours do count toward the 1,500 hour total time requirement, but not several of the other requirements. From 14 CFR 61.159 (parts in bold are where I've highlighted those requirements that must be met in an airplane category, i.e. not a glider).

Presumably you're also not logging much instrument flight time in gliders, so I didn't highlight that.


  § 61.159 Aeronautical experience: Airplane category rating.
  
  (a) Except as provided in paragraphs (b), (c), and (d) of this section, a person who is applying for an airline transport pilot certificate with an airplane category and class rating must have at least 1,500 hours of total time as a pilot that includes at least:
  
  
    (1) 500 hours of cross-country flight time.
    
    (2) 100 hours of night flight time.
    
    (3) 50 hours of flight time in the class of airplane for the rating sought. A maximum of 25 hours of training in a full flight simulator representing the class of airplane for the rating sought may be credited toward the flight time requirement of this paragraph if the training was accomplished as part of an approved training course in parts 121, 135, 141, or 142 of this chapter. A flight training device or aviation training device may not be used to satisfy this requirement.
    
    (4) 75 hours of instrument flight time, in actual or simulated instrument conditions, subject to the following:
    
    
      (i) Except as provided in paragraph (a)(4)(ii) of this section, an applicant may not receive credit for more than a total of 25 hours of simulated instrument time in a flight simulator or flight training device.
      
      (ii) A maximum of 50 hours of training in a flight simulator or flight training device may be credited toward the instrument flight time requirements of paragraph (a)(4) of this section if the training was accomplished in a course conducted by a training center certificated under part 142 of this chapter.
      
      (iii) Training in a flight simulator or flight training device must be accomplished in a flight simulator or flight training device, representing an airplane.
    
    
    (5) 250 hours of flight time in an airplane as a pilot in command, or as second in command performing the duties of pilot in command while under the supervision of a pilot in command, or any combination thereof, which includes at least -
    
    
      (i) 100 hours of cross-country flight time; and
      
      (ii) 25 hours of night flight time.
      
      (6) Not more than 100 hours of the total aeronautical experience requirements of paragraph (a) of this section or § 61.160 may be obtained in a full flight simulator or flight training device provided the device represents an airplane and the aeronautical experience was accomplished as part of an approved training course in parts 121, 135, 141, or 142 of this chapter.
    
  
  
  (b) A person who has performed at least 20 night takeoffs and landings to a full stop may substitute each additional night takeoff and landing to a full stop for 1 hour of night flight time to satisfy the requirements of paragraph (a)(2) of this section; however, not more than 25 hours of night flight time may be credited in this manner.
  
  (c) A commercial pilot may credit the following second-in-command flight time or flight-engineer flight time toward the 1,500 hours of total time as a pilot required by paragraph (a) of this section:
  
  
    (1) Second-in-command time, provided the time is acquired in an airplane -
    
    
      (i) Required to have more than one pilot flight crewmember by the airplane's flight manual, type certificate, or the regulations under which the flight is being conducted;
      
      (ii) Engaged in operations under subpart K of part 91, part 121, or part 135 of this chapter for which a second in command is required; or
      
      (iii) That is required by the operating rules of this chapter to have more than one pilot flight crewmember.
    
    
    (2) Flight-engineer time, provided the time -
    
    
      (i) Is acquired in an airplane required to have a flight engineer by the airplane's flight manual or type certificate;
      
      (ii) Is acquired while engaged in operations under part 121 of this chapter for which a flight engineer is required;
      
      (iii) Is acquired while the person is participating in a pilot training program approved under part 121 of this chapter; and
      
      (iv) Does not exceed more than 1 hour for each 3 hours of flight engineer flight time for a total credited time of no more than 500 hours.
    
    
    (3) Flight-engineer time, provided the flight time -
    
    
      (i) Is acquired as a U.S. Armed Forces' flight engineer crewmember in an airplane that requires a flight engineer crewmember by the flight manual;
      
      (ii) Is acquired while the person is participating in a flight engineer crewmember training program for the U.S. Armed Forces; and
      
      (iii) Does not exceed 1 hour for each 3 hours of flight engineer flight time for a total credited time of no more than 500 hours.
    
  
  
  (d) An applicant is issued an airline transport pilot certificate with the limitation, “Holder does not meet the pilot in command aeronautical experience requirements of ICAO,” as prescribed under Article 39 of the Convention on International Civil Aviation, if the applicant does not meet the ICAO requirements contained in Annex 1 “Personnel Licensing” to the Convention on International Civil Aviation, but otherwise meets the aeronautical experience requirements of this section.
  
  (e) An applicant is entitled to an airline transport pilot certificate without the ICAO limitation specified under paragraph (d) of this section when the applicant presents satisfactory evidence of having met the ICAO requirements under paragraph (d) of this section and otherwise meets the aeronautical experience requirements of this section.